Chromium bicyclic phosphinyl amidine complexes for tetramerization of ethylene

ABSTRACT

The present disclosure relates to a catalyst system comprising i) (a) an N 2 -phosphinyl bicyclic amidine chromium salt or (b) a chromium salt and an N 2 -phosphinyl bicyclic amidine and ii) an organoaluminum compound. The present disclosure also relate to a process comprising: a) contacting i) ethylene; ii) a catalyst system comprising (a) an N 2 -phosphinyl bicyclic amidine chromium salt complex or (b) a chromium salt and an N 2 -phosphinyl bicyclic amidine; ii) an organoaluminum compound, and iii) optionally an organic reaction medium; and b) forming an oligomer product in a reaction zone.

TECHNICAL FIELD

This disclosure relates to catalyst systems comprising N²-phosphinylbicyclic amidine and a chromium salt or a N²-phosphinyl bicyclic amidinechromium salt complex. The disclosure also relates to using the catalystsystems comprising the N²-phosphinyl bicyclic amidine and a chromiumsalt or the N²-phosphinyl bicyclic amidine chromium salt complex in theoligomerization of ethylene.

BACKGROUND

Olefins, also commonly known as alkenes, are important items ofcommerce. Their many applications include employment as intermediates inthe manufacture of detergents, as precursors to more environmentallyfriendly refined oils, as monomers, and as precursors for many othertypes of products. An important subset of olefins is alpha olefins. Onemethod of making alpha olefins is via oligomerization of ethylene, whichis a catalytic reaction involving various types of catalysts and/orcatalyst systems. Examples of catalysts and catalyst systems usedcommercially in the oligomerization of ethylene include alkylaluminumcompounds, certain nickel-phosphine complexes, a titanium halide with aLewis acid (e.g., diethyl aluminum chloride), a selective 1-hexenecatalyst system containing a chromium containing compound (e.g., achromium carboxylate), a nitrogen containing ligand (e.g., a pyrrole), ametal alkyl (e.g., alkyl aluminum compounds), and selectivetrimerization and/or tetramerization catalyst systems using a metalcomplex of a compound having a diphosphinylaminyl group.

Several non-commercial ethylene oligomerization catalyst systems arebased upon metal complexes of pyridine bis-imines, and metal complexesof α-diimine compounds having a metal complexing group. These catalystsystems typically use an alkyl aluminum compound (e.g., aluminoxane) toactivate the metal complexes for olefin oligomerization.

Applications and demand for olefins (e.g., alpha olefins) continue tomultiply, and competition to supply them correspondingly intensifies.Thus, additional novel and improved catalyst systems and methods forethylene oligomerization are desirable.

SUMMARY

Disclosed herein is a catalyst system comprising i) (a) an N²-phosphinylbicyclic amidine chromium salt complex having Structure NPBACr I orStructure NPBACr II

or (b) a chromium salt and an N²-phosphinyl bicyclic amidine havingStructure NBPA I or Structure NPBA II

wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently can bea hydrogen or a C₁ to C₃₀ organyl group, L¹ and L² independently can bea C₁ to C₃₀ a hydrocarbylene group, R⁴ and R⁵ independently can be a C₁to C₃₀ organyl group and R⁴ and R⁵ optionally can be combined to formL⁴⁵ forming a ring or ring system including the phosphorus atom whereL⁴⁵ can be a C₁ to C₃₀ organylene group, and CrX_(p) is a chromium saltwhere X is a monoanion and p is an integer from 2 to 6; and ii) anorganoaluminum compound.

Also disclosed herein is a process comprising: a) contacting i)ethylene; ii) a catalyst system comprising (a) (i) an N²-phosphinylbicyclic amidine chromium salt complex having Structure NPBACr I and/orStructure NPBACr II

or (ii) a chromium salt and an N²-phosphinyl bicyclic amidine havingStructure NPBA I or Structure NPBA II

wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently can bea hydrogen or a C₁ to C₃₀ organyl group, L¹ and L² independently can bea C₁ to C₃₀ a hydrocarbylene group, R⁴ and R⁵ independently can be a C₁to C₃₀ organyl group and R⁴ and R⁵ optionally can be combined to formL⁴⁵ forming a ring or ring system including the phosphorus atom whereL⁴⁵ can be a C₁ to C₃₀ organylene group, and CrX_(p) is a chromium saltwhere X is a monoanion and p is an integer from 2 to 6; (b) anorganoaluminum compound, and iii) optionally an organic reaction medium;and b) forming an oligomer product in a reaction zone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot the calculated Gibbs free energy difference, ΔΔG^(‡),between the transition states leading to 1-hexene and 1-octene versusthe natural logarithm of the quantity of 1-hexene and 1-octene(ln(C₆/C₈)) for five experimentally evaluated ethylene oligomerizationsusing five N²-phosphinylamidine chromium salt complex catalyst systemsand the predictive values ΔΔG^(‡).

DETAILED DESCRIPTION

To define more clearly the terms used herein, the following definitionsare provided. Unless otherwise indicated, the following definitions areapplicable to this disclosure. If a term is used in this disclosure butis not specifically defined herein, the definition from the IUPACCompendium of Chemical Terminology, 2^(nd) Ed (1997) can be applied, aslong as that definition does not conflict with any other disclosure ordefinition applied herein, or render indefinite or non-enabled any claimto which that definition is applied. To the extent that any definitionor usage provided by any document incorporated herein by referenceconflicts with the definition or usage provided herein, the definitionor usage provided herein controls.

Groups of elements of the periodic table are indicated using thenumbering scheme indicated in the version of the periodic table ofelements published in Chemical and Engineering News, 63(5), 27, 1985. Insome instances, a group of elements can be indicated using a common nameassigned to the group; for example alkali earth metals (or alkalimetals) for Group 1 elements, alkaline earth metals (or alkaline metals)for Group 2 elements, transition metals for Group 3-12 elements, andhalogens for Group 17 elements.

Regarding claim transitional terms or phrases, the transitional term“comprising”, which is synonymous with “including,” “containing,”“having,” or “characterized by,” is inclusive or open-ended and does notexclude additional, unrecited elements or method steps. The transitionalphrase “consisting of” excludes any element, step, or ingredient notspecified in the claim. The transitional phrase “consisting essentiallyof” limits the scope of a claim to the specified materials or steps andthose that do not materially affect the basic and novelcharacteristic(s) of the subject matter described herein. A “consistingessentially of” claim occupies a middle ground between closed claimsthat are written in a “consisting of” format and fully open claims thatare drafted in a “comprising” format. Absent an indication to thecontrary, when describing a compound or composition “consistingessentially of” is not to be construed as “comprising,” but is intendedto describe the recited component that includes materials which do notsignificantly alter the composition or method to which the term isapplied. For example, a feedstock consisting essentially of a material Acan include impurities typically present in a commercially produced orcommercially available sample of the recited compound or composition.When a claim includes different features and/or feature classes (forexample, a method step, feedstock features, and/or product features,among other possibilities), the transitional terms “comprising,”“consisting essentially of,” and “consisting of” apply only to thefeature class which is utilized and it is possible to have differenttransitional terms or phrases utilized with different features within aclaim. For example, a method can comprise several recited steps (andother non-recited steps) but utilize a catalyst system preparationconsisting of specific steps; or alternatively, consist of specificsteps and/or utilize a catalyst system comprising recited components andother non-recited components.

Within this specification, use of “comprising” or an equivalentexpression contemplates the use of the phrase “consisting essentiallyof,” “consists essentially of,” or equivalent expressions as alternativeaspects to the open-ended expression. Additionally, use of “comprising”or an equivalent expression or use of “consisting essentially of” in thespecification contemplates the use of the phrase “consisting of,”“consists of,” or equivalent expressions as an alternative to theopen-ended expression or middle ground expression, respectively. Forexample, “comprising” should be understood to include “consistingessentially of,” and “consisting of” as alternative aspects for theaspect, features, and/or elements presented in the specification unlessspecifically indicated otherwise.

While compositions and methods are described in terms of “comprising”various components or steps, the compositions and methods can also“consist essentially of” or “consist of” the various components orsteps.

The terms “a,” “an,” and “the” are intended, unless specificallyindicated otherwise, to include plural alternatives, e.g., at least one.For instance, the disclosure of “a trialkylaluminum compound” is meantto encompass one trialkylaluminum compound, or mixtures or combinationsof more than one trialkylaluminum compound unless otherwise specified.

For any particular compound disclosed herein, the general structure orname presented is also intended to encompass all structural isomers,conformational isomers, and stereoisomers that can arise from aparticular set of substituents, unless indicated otherwise. Thus, ageneral reference to a compound includes all structural isomers unlessexplicitly indicated otherwise; e.g., a general reference to pentaneincludes n-pentane, 2-methyl-butane, and 2,2-dimethylpropane while ageneral reference to a butyl group includes an n-butyl group, asec-butyl group, an iso-butyl group, and a tert-butyl group.Additionally, the reference to a general structure or name encompassesall enantiomers, diastereomers, and other optical isomers whether inenantiomeric or racemic forms, as well as mixtures of stereoisomers, asthe context permits or requires. For any particular formula or name thatis presented, any general formula or name presented also encompasses allconformational isomers, regioisomers, and stereoisomers that can arisefrom a particular set of substituents.

A chemical “group” is described according to how that group is formallyderived from a reference or “parent” compound, for example, by thenumber of hydrogen atoms formally removed from the parent compound togenerate the group, even if that group is not literally synthesized inthis manner. These groups can be utilized as substituents or coordinatedor bonded to metal atoms. By way of example, an “alkyl group” formallycan be derived by removing one hydrogen atom from an alkane, while an“alkylene group” formally can be derived by removing two hydrogen atomsfrom an alkane. Moreover, a more general term can be used to encompass avariety of groups that formally are derived by removing any number (“oneor more”) of hydrogen atoms from a parent compound, which in thisexample can be described as an “alkane group,” and which encompasses an“alkyl group,” an “alkylene group,” and materials having three or morehydrogens atoms, as necessary for the situation, removed from thealkane. Throughout, the disclosure that a substituent, ligand, or otherchemical moiety can constitute a particular “group” implies that thewell-known rules of chemical structure and bonding are followed whenthat group is employed as described. When describing a group as being“derived by,” “derived from,” “formed by,” or “formed from,” such termsare used in a formal sense and are not intended to reflect any specificsynthetic methods or procedure, unless specified otherwise or thecontext requires otherwise.

The term “substituted” when used to describe a group, for example, whenreferring to a substituted analog of a particular group, is intended todescribe any non-hydrogen moiety that formally replaces a hydrogen inthat group, and is intended to be non-limiting. A group or groups canalso be referred to herein as “unsubstituted” or by equivalent termssuch as “non-substituted,” which refers to the original group in which anon-hydrogen moiety does not replace a hydrogen within that group.“Substituted” is intended to be non-limiting and include inorganicsubstituents or organic substituents.

An N²-phosphinyl bicyclic amidine refers a amidine compound where thetwo nitrogen atoms of the N²-phosphinyl amidine group are in separaterings of a bicyclic ring system.

The term “organyl group” is used herein in accordance with thedefinition specified by IUPAC: an organic substituent group, regardlessof functional type, having one free valence at a carbon atom. Similarly,an “organylene group” refers to an organic group, regardless offunctional type, derived by removing two hydrogen atoms from an organiccompound, either two hydrogen atoms from one carbon atom or one hydrogenatom from each of two different carbon atoms. An “organic group” refersto a generalized group formed by removing one or more hydrogen atomsfrom carbon atoms of an organic compound. Thus, an “organyl group,” an“organylene group,” and an “organic group” can contain organicfunctional group(s) and/or atom(s) other than carbon and hydrogen, thatis, an organic group can comprise functional groups and/or atoms inaddition to carbon and hydrogen. “Organyl groups,” “organylene groups,”and “organic groups” can be aliphatic (inclusive of being cyclic oracyclic, or linear or branched) or can be aromatic.

For the purposes of this application, the term or variations of the term“organyl group consisting of inert functional groups” refers to anorganyl group wherein the organic functional group(s) and/or atom(s)other than carbon and hydrogen present in the functional group arerestricted to those functional group(s) and/or atom(s) other than carbonand hydrogen which do not complex with a metal compound and/or are inertunder the process conditions defined herein. Thus, the term or variationof the term “organyl group consisting of inert functional groups”further defines the particular organyl groups that can be present withinthe organyl group consisting of inert functional groups. Additionally,the term “organyl group consisting of inert functional groups” can referto the presence of one or more inert functional groups within theorganyl group. The term or variation of the term “organyl groupconsisting of inert functional groups” includes the hydrocarbyl group asa member (among other groups). Similarly, an “organylene groupconsisting of inert functional groups” refers to an organic group formedby removing two hydrogen atoms from one or two carbon atoms of anorganic compound consisting of inert functional groups and an “organicgroup consisting of inert functional groups” refers to a generalizedorganic group consisting of inert functional groups formed by removingone or more hydrogen atoms from one or more carbon atoms of an organiccompound consisting of inert functional groups.

For purposes of this application, an “inert functional group” is a groupwhich does not substantially interfere with the process described hereinin which the material having an inert functional group takes part and/ordoes not complex with the metal compound of the metal complex. The term“does not complex with the metal compound” can include groups that couldcomplex with a metal compound but in particular molecules describedherein may not complex with a metal compound due to its positionalrelationship within a ligand. For example, while an ether group cancomplex with a metal compound, an ether group located at a para positionof a substituted phenyl phosphinyl group in an N²-phosphinyl amidine canbe an inert functional group because a single metal compound cannotcomplex with both the para ether group and the N²-phosphinyl amidinegroup of the same metal complex molecule. Thus, the inertness of aparticular functional group is not only related to the functionalgroup's inherent inability to complex the metal compound but can also berelated to the functional group's position within the metal complex.Non-limiting examples of inert functional groups which do notsubstantially interfere with processes described herein can include halo(fluoro, chloro, bromo, and iodo), nitro, hydrocarboxy groups (e.g.,alkoxy, and/or aroxy, among others), sulfidyl groups, and/or hydrocarbylgroups, among others.

The term “hydrocarbon” whenever used in this specification and claimsrefers to a compound containing only carbon and hydrogen. Otheridentifiers can be utilized to indicate the presence of particulargroups in the hydrocarbon (e.g., halogenated hydrocarbon indicates thepresence of one or more halogen atoms replacing an equivalent number ofhydrogen atoms in the hydrocarbon). The term “hydrocarbyl group” is usedherein in accordance with the definition specified by IUPAC: a univalentgroup formed by removing a hydrogen atom from a hydrocarbon. Similarly,a “hydrocarbylene group” refers to a group formed by removing twohydrogen atoms from a hydrocarbon, either two hydrogen atoms from onecarbon atom or one hydrogen atom from each of two different carbonatoms. Therefore, in accordance with the terminology used herein, a“hydrocarbon group” refers to a generalized group formed by removing oneor more hydrogen atoms (as necessary for the particular group), from ahydrocarbon. A “hydrocarbyl group,” “hydrocarbylene group,” and“hydrocarbon group” can be acyclic or cyclic groups, and/or can belinear or branched. A “hydrocarbyl group,” “hydrocarbylene group,” and“hydrocarbon group” can include rings, ring systems, aromatic rings, andaromatic ring systems, which contain only carbon and hydrogen.“Hydrocarbyl groups,” “hydrocarbylene groups,” and “hydrocarbon groups”include, by way of example, aryl, arylene, arene, alkyl, alkylene,alkane, cycloalkyl, cycloalkylene, cycloalkane, aralkyl, aralkylene, andaralkane groups, among other groups, as members.

The term “alkane” whenever used in this specification and claims refersto a saturated hydrocarbon compound. Other identifiers can be utilizedto indicate the presence of particular groups in the alkane (e.g.,halogenated alkane indicates the presence of one or more halogen atomsreplacing an equivalent number of hydrogen atoms in the alkane). Theterm “alkyl group” is used herein in accordance with the definitionspecified by IUPAC: a univalent group formed by removing a hydrogen atomfrom an alkane. Similarly, an “alkylene group” refers to a group formedby removing two hydrogen atoms from an alkane (either two hydrogen atomsfrom one carbon atom or one hydrogen atom from two different carbonatoms). An “alkane group” is a general term that refers to a groupformed by removing one or more hydrogen atoms (as necessary for theparticular group) from an alkane. An “alkyl group,” “alkylene group,”and “alkane group” can be acyclic or cyclic groups, and/or can be linearor branched unless otherwise specified. Primary, secondary, and tertiaryalkyl groups are derived by removal of a hydrogen atom from a primary,secondary, or tertiary carbon atom, respectively, of an alkane. Then-alkyl group can be derived by removal of a hydrogen atom from aterminal carbon atom of a linear alkane.

A cycloalkane is a saturated cyclic hydrocarbon, with or without sidechains, for example, cyclobutane. Unsaturated cyclic hydrocarbons havingone or more endocyclic double or one triple bond are called cycloalkenesand cycloalkynes, respectively. Cycloalkenes and cycloalkynes havingonly one, only two, only three, etc. endocyclic double or triple bonds,respectively, can be identified by use of the term “mono,” “di,” “tri,”etc. . . . within the name of the cycloalkene or cycloalkyne.Cycloalkenes and cycloalkynes can further identify the position of theendocyclic double or triple bonds.

The term “substituted” when used to describe a compound or group, forexample, when referring to a substituted analog of a particular compoundor group, is intended to describe any non-hydrogen moiety that formallyreplaces a hydrogen in that group, and is intended to be non-limiting. Agroup or groups can also be referred to herein as “unsubstituted” or byequivalent terms such as “non-substituted,” which refers to the originalgroup in which a non-hydrogen moiety does not replace a hydrogen withinthat group. “Substituted” is intended to be non-limiting and includeinorganic substituents or organic substituents.

The term “olefin” whenever used in this specification and claims refersto hydrocarbons that have at least one carbon-carbon double bond that isnot part of an aromatic ring or ring system. The term “olefin” includesaliphatic and aromatic, acyclic and cyclic, and/or linear and branchedcompounds having at least one carbon-carbon double bond that is not partof an aromatic ring or ring system unless specifically stated otherwise.Olefins having only one, only two, only three, etc. carbon-carbon doublebonds can be identified by use of the term “mono,” “di,” “tri,” etc. . .. within the name of the olefin. The olefins can be further identifiedby the position of the carbon-carbon double bond(s).

The term “alkene” whenever used in this specification and claims refersa linear or branched hydrocarbon olefin that has one or morecarbon-carbon double bonds. Alkenes having only one, only two, onlythree, etc. such multiple bonds can be identified by use of the term“mono,” “di,” “tri,” etc. . . . within the name. Alkenes can be furtheridentified by the position of the carbon-carbon double bond(s). Otheridentifiers can be utilized to indicate the presence or absence ofparticular groups within an alkene. For example, a haloalkene refers toan alkene having one or more hydrogen atoms replaced with a halogenatom.

The term “alpha olefin” as used in this specification and claims refersto an olefin that has a carbon-carbon double bond between the first andsecond carbon atom of the longest contiguous chain of carbon atoms. Theterm “alpha olefin” includes linear and branched alpha olefins unlessexpressly stated otherwise. In the case of branched alpha olefins, abranch can be at the 2 position (a vinylidene) and/or the 3 position orhigher with respect to the olefin double bond. The term “vinylidene”whenever used in this specification and claims refers to an alpha olefinhaving a branch at the 2 position with respect to the olefin doublebond. By itself, the term “alpha olefin” does not indicate the presenceor absence of other carbon-carbon double bonds unless explicitlyindicated. The term “linear alpha olefin” as used herein refers to anon-branched alpha olefin having a carbon-carbon double bond between thefirst and second carbon atom.

The term “normal alpha olefin” whenever used in this specification andclaims refers to a linear hydrocarbon mono-olefin having a carbon-carbondouble bond between the first and second carbon atom. It is noted that“normal alpha olefin” is not synonymous with “linear alpha olefin” asthe term “linear alpha olefin” can include linear olefinic compoundshaving a double bond between the first and second carbon atoms andadditional double bonds.

An aliphatic compound is an acyclic or cyclic, saturated or unsaturatedcarbon compound, excluding aromatic compounds. Thus, an aliphaticcompound is an acyclic or cyclic, saturated or unsaturated carboncompound, excluding aromatic compounds; that is, an aliphatic compoundis a non-aromatic organic compound. An “aliphatic group” is ageneralized group formed by removing one or more hydrogen atoms (asnecessary for the particular group) from the carbon atom of an aliphaticcompound. Aliphatic compounds and therefore aliphatic groups can containorganic functional group(s) and/or atom(s) other than carbon andhydrogen.

An aromatic compound is a compound containing a cyclically conjugateddouble bond system that follows the Hückel (4n+2) rule and contains(4n+2) pi-electrons, where n is an integer from 1 to 5. Aromaticcompounds include “arenes” (hydrocarbon aromatic compounds) and“heteroarenes,” also termed “hetarenes” which are heteroaromaticcompounds formally derived from arenes by replacement of one or moremethine (—C═) carbon atoms of the cyclically conjugated double bondsystem with a trivalent or divalent heteroatom, in such a way as tomaintain the continuous pi-electron system characteristic of an aromaticsystem and a number of out-of-plane pi-electrons corresponding to theHückel rule (4n+2). While arene compounds and heteroarene compounds aremutually exclusive members of the group of aromatic compounds, acompound that has both an arene group and a heteroarene group isgenerally considered a heteroarene compound. Aromatic compounds, arenes,and heteroarenes can be monocyclic (e.g., benzene, toluene, furan,pyridine, methylpyridine) or polycyclic unless otherwise specified.Polycyclic aromatic compounds, arenes, and heteroarenes, include, unlessotherwise specified, compounds wherein the aromatic rings can be fused(e.g., naphthalene, benzofuran, and indole), compounds where thearomatic groups can be separate and joined by a bond (e.g., biphenyl or4-phenylpyridine), or compounds where the aromatic groups are joined bya group containing linking atoms (e.g., carbon in the methylene group indiphenylmethane; oxygen in diphenyl ether; nitrogen in triphenyl amine;among other linking groups). As disclosed herein, the term “substituted”can be used to describe an aromatic group, arene, or heteroarene whereina non-hydrogen moiety formally replaces a hydrogen in the compound andis intended to be non-limiting.

An “aromatic group” refers to a generalized group formed by removing oneor more hydrogen atoms (as necessary for the particular group and atleast one of which is an aromatic ring carbon atom) from an aromaticcompound. For a univalent “aromatic group,” the removed hydrogen atommust be from an aromatic ring carbon. For an “aromatic group” formed byremoving more than one hydrogen atom from an aromatic compound, at leastone hydrogen atom must be from an aromatic hydrocarbon ring carbon.Additionally, an “aromatic group” can have hydrogen atoms removed fromthe same ring of an aromatic ring or ring system (e.g., phen-1,4-ylene,pyridin-2,3-ylene, naphth-1,2-ylene, and benzofuran-2,3-ylene), hydrogenatoms removed from two different rings of a ring system (e.g.,naphth-1,8-ylene and benzofuran-2,7-ylene), or hydrogen atoms removedfrom two isolated aromatic rings or ring systems (e.g.,bis(phen-4-ylene)methane).

An “aryl compound” refers to an aromatic hydrocarbon. An “aryl group”refers to univalent aromatic hydrocarbon having a free valance at anaromatic ring carbon atom. Similarly, a “arylene group” refers to agroup derived by removing two hydrogen atoms from an aromatichydrocarbon, at least one of which is an aromatic ring carbon. Thus, an“arylene group” includes both a group derived from an aromatichydrocarbon in which two hydrogen atoms are formally removed from thesame aromatic ring carbon, a group derived from an aromatic hydrocarbonin which two hydrogen atoms are formally removed from two differentaromatic ring carbons, and a group derived from an aromatic hydrocarbonin which a first hydrogen atom is formally removed from an aromatic ringcarbon and a second hydrogen atom is formally removed from a carbon atomthat is not an aromatic ring carbon. An “aromatic hydrocarbon group”refers to a generalized group formed by removing one or more hydrogenatoms (as necessary for the particular group and at least one of whichis an aromatic ring carbon) from an aromatic hydrocarbon compound.

An “arylalkane” refers to an aromatic hydrocarbon having at least onealkyl group substituent. An “aralkyl group” is an aryl-substituted alkylgroup having a free valance at a non-aromatic carbon atom of anarylalkane (e.g., a benzyl group, or a 2-phenyleth-lyl group, amongothers). Similarly, an “aralkylene group” is an aryl-substitutedalkylene group having two free valencies at a single non-aromatic carbonatom of an arylalkane or a free valence at two non-aromatic carbon atomsof an arylalkane while an “aralkane group” is an aryl-substituted alkanegroup having one or more free valencies at a non-aromatic carbon atom(s)of an arylalkane. It should be noted that according the definitionsprovided herein, general aralkane groups include those having zero, one,or more than one hydrocarbyl substituent groups located on an aralkanearomatic hydrocarbon ring or ring system carbon atom and are members ofthe group of hydrocarbon groups. However, specific aralkane groupsspecifying a particular aryl group (e.g., the phenyl group in a benzylgroup or a 2-phenylethyl group, among others) refer to the specificunsubstituted aralkane groups (including no hydrocarbyl group located onthe aralkane aromatic hydrocarbon ring or ring system carbon atom).Consequently, a substituted aralkane group specifying a particular arylgroup refers to a respective aralkane group having one or moresubstituent groups (including halogens, hydrocarbyl groups, orhydrocarboxy groups, among others). When the substituted aralkane groupspecifying a particular aryl group is a member of the group ofhydrocarbon groups (or a member of the general group of aralkanegroups), each substituent is limited to a hydrocarbyl substituent group.One can readily discern and select substituted aralkane groupsspecifying a particular aryl group which can be utilized as a member ofthe group of hydrocarbon groups (or a member of the general group ofaralkane groups).

A “halide” has its usual meaning; therefore, examples of halides includefluoride, chloride, bromide, and iodide.

Within this specification, the word “reactor” refers to a single pieceof equipment, such as, for example, a vessel, in which a reaction takesplace, but excludes any associated equipment such as piping, pumps, andthe like which is external to the vessel. Examples of reactors includestirred tank reactors (e.g., a continuous stirred tank reactor), plugflow reactors, or any other type of reactor. Within this specification“reaction zone” refers to any portion of equipment in which a desiredreaction occurs, including but not limited to, a reactor, associatedpiping, associated pumps, and any other associated equipment. It shouldbe noted that in some cases a “reactor” can also be a “reaction zone.”The terms “reactor” and “reaction zone” can be qualified to refer tomore specific “reactors” and “reaction zone” by use of additionalqualifying terms. For example, the use of the term use of the term“oligomerization reactor” and “oligomerization reaction zone” indicatesthat the desired reaction within the reactor and/or reaction zone is anoligomerization reaction.

Within this specification, term “reaction zone” refers to the portion ofa process, the associated equipment and associated process lines whereall the necessary reaction components and reaction conditions arepresent such that the reaction can occur at a desired rate. That is tosay that the reaction zone begins where the necessary reactioncomponents and reaction conditions are present to maintain the reactionwithin 25 percent of the average reaction rate and the reaction systemends where the conditions do not maintain a reaction rate within 25percent of the average reaction rate (based upon a volume average of thereaction rate of the reaction system). For example, in terms of anoligomerization process, the reaction zone begins at the point wheresufficient feedstock and active catalyst system is present under thesufficient reaction conditions to maintain oligomer product productionat the desired rate and the reaction zone ends at a point where eitherthe catalyst system is deactivated, sufficient feedstock is not presentto sustain oligomer product production, or other reaction conditions arenot sufficient to maintain the oligomer product production or thedesired oligomer product production rate. Within this specification the“reaction zone” can comprise one or more reactor zone, one or morereactors, and associated equipment where all the necessary reactioncomponents and reaction conditions are present such that the reactioncan occur at a desired rate. The use of the term “oligomerizationreaction zone” indicates that the desired reaction within the reactionzone is an oligomerization reaction.

The terms “room temperature” or “ambient temperature” are used herein todescribe any temperature from 15° C. to 35° C. wherein no external heator cooling source is directly applied. Accordingly, the terms “roomtemperature” and “ambient temperature” encompass the individualtemperatures and any and all ranges, subranges, and combinations ofsubranges of temperatures from 15° C. to 35° C. wherein no externalheating or cooling source is directly applied. The term “atmosphericpressure” is used herein to describe an earth air pressure wherein noexternal pressure modifying means is utilized. Generally, unlesspracticed at extreme earth altitudes, “atmospheric pressure” is about 1atmosphere (alternatively, about 14.7 psi or about 101 kPa). Referencesto gaseous, liquid, and/or solid materials refer to the physical stateof the material at 25° C. and atmospheric pressure unless otherwisespecified.

Features within this disclosure that are provided as minimum values canbe alternatively stated as “at least” or “greater than or equal to” anyrecited minimum value for the feature disclosed herein. Features withinthis disclosure that are provided as maximum values can be alternativelystated as “less than or equal to” for the feature disclosed herein.

Within this disclosure, the normal rules of organic nomenclature willprevail. For instance, when referencing substituted compounds or groups,references to substitution patterns are taken to indicate that theindicated group(s) is (are) located at the indicated position and thatall other non-indicated positions are hydrogen. For example, referenceto a 4-substituted phenyl group indicates that there is a non-hydrogensubstituent located at the 4 position and hydrogens located at the 2, 3,5, and 6 positions. By way of another example, reference to a3-substituted naphth-2-yl indicates that there is a non-hydrogensubstituent located at the 3 position and hydrogens located at the 1, 4,5, 6, 7, and 8 positions. References to compounds or groups havingsubstitutions at positions in addition to the indicated position will bereferenced using “comprising” or some other alternative language. Forexample, a reference to a phenyl group comprising a substituent at the 4position refers to a group having a non-hydrogen atom at the 4 positionand hydrogen or any non-hydrogen group at the 2, 3, 5, and 6 positions.

Processes for forming oligomer products are described herein. Suchprocesses generally comprise contacting ethylene and a catalyst system(or alternatively, contacting ethylene and the components of thecatalyst system) to form an oligomer product under oligomerizationconditions.

The term “reaction zone effluent” and its derivatives (e.g.,oligomerization reaction zone effluent, trimerization reaction zoneeffluent, tetramerization reaction zone effluent, or trimerization andtetramerization reaction zone effluent) generally refers to allmaterials which exit the reaction zone. The materials that can exit thereaction zone include reaction feed(s) (e.g., ethylene, catalyst systemor catalyst system components, and/or organic reaction medium), and/orreaction product(s) (e.g., oligomer product including oligomers andnon-oligomers). The term “reaction zone effluent” and its derivativescan be qualified to refer to certain portions by use of additionalqualifying terms. For example, while reaction zone effluent refers toall materials which exits the reaction zone, a reaction zone oligomerproduct effluent refers to only the oligomer product within the reactionzone effluent.

The term “oligomerization,” and its derivatives, refers to processeswhich produce a mixture of products containing at least 70 weightpercent products containing from 2 to 30 ethylene units. Similarly, asused herein an “oligomer” is a product that contains from 2 to 30ethylene units while an “oligomerization product” or “oligomer product”includes all products made by the process including the “oligomers” andproducts which are not “oligomers” (e.g., products which contain morethan 30 ethylene units). Further the terms “oligomer product” and“oligomerization product” can be used interchangeably.

The term “trimerization,” and its derivatives, refers to a process whichproduces a mixture of products containing at least 70 weight percentproducts containing three and only three ethylene units. A “trimer” is aproduct which contains three and only three ethylene units while a“trimerization product” includes all products made by the trimerizationprocess including trimers and products which are not trimers (e.g.,dimers or tetramers). Generally, a “trimerization” process usingethylene produces an oligomer product containing at least 70 weightpercent hexene(s).

The term “tetramerization,” and its derivatives, refers to a processwhich produces a mixture of products containing at least 70 weightpercent products containing four and only four ethylene units. A“tetramer” is a product which contains four and only four ethylene unitswhile a “tetramerization product” includes all products made by thetetramerization process including tetramers and products which are nottetramers (e.g., dimers or trimers). Generally, a “tetramerization”process using ethylene produces an oligomer product containing at least70 weight percent octene(s).

The term “trimerization and tetramerization,” and its derivatives,refers to a process which produces a mixture of products containing atleast 70 weight percent products containing three and/or four and onlythree and/or four ethylene units. A “trimerization and tetramerizationproduct” includes all products made by the “trimerization andtetramerization” process including trimers, tetramers, and productswhich are not trimers or tetramers (e.g., dimers). Generally, a“trimerization and tetramerization” process using ethylene produces anoligomer product containing at least 70 weight percent hexene(s) and/oroctene(s).

Unless otherwise specified, the terms “contacted,” “combined,” and “inthe presence of” refer to any addition sequence, order, or concentrationfor contacting or combining two or more components of the process.Combining or contacting of components, according to the various methodsdescribed herein, can occur in one or more contact zones under suitablecontact conditions such as temperature, pressure, contact time, flowrates, etc. The contact zone can be disposed in a vessel (e.g., astorage tank, tote, container, mixing vessel, reactor, etc.), a lengthof pipe (e.g., a tee, inlet, injection port, or header for combiningcomponent feed lines into a common line), or any other suitableapparatus for bringing the components into contact. The processes can becarried out in a batch or continuous process as can be suitable for agiven aspect.

Use of the term “optionally” with respect to any element of a claim isintended to mean that the subject element is required, or alternatively,is not required. Both alternatives are intended to be within the scopeof the claim.

Processes described herein can utilize steps, features, compounds and/orequipment which are independently described herein. The processesdescribed herein may or may not utilize step identifiers (e.g., 1), 2),etc., a), b), etc., i), ii), etc., or first, second, etc., amongothers), feature identifiers (e.g., 1), 2), etc., a), b), etc., i), ii),etc., or first, second, etc., among others), and/or compound and/orcomposition identifiers (e.g., 1), 2), etc., a), b), etc., i), ii),etc., or first, second, etc., among others). However, it should be notedthat processes described herein can have multiple steps, features (e.g.,reagent ratios, formation conditions, among other considerations),and/or multiple compounds and/or compositions using no descriptor orsometimes having the same general identifier. Consequently, it should benoted that the processes described herein can be modified to use anappropriate step or feature identifier (e.g., 1), 2), etc., a), b),etc., i), ii), etc., or first, second, etc., among others), featureidentifier (e.g., 1), 2), etc., a), b), etc., i), ii), etc., or first,second, etc., among others), and/or compound identifier (e.g., first,second, etc.) regardless of step, feature, and/or compound identifierutilized in a particular aspect described herein and that step orfeature identifiers can be added and/or modified to indicate individualdifferent steps/features/compounds utilized within the processes withoutdetracting from the general disclosure.

The present disclosure relates to catalyst systems comprising anN²-phosphinyl bicyclic amidine chromium salt complex; or alternatively,an N²-phosphinyl bicyclic amidine and a chromium salt. In an aspect, thecatalyst system can comprise, or consist essentially of, anN²-phosphinyl bicyclic amidine chromium salt complex and anorganoaluminum compound; or alternatively, an N²-phosphinyl bicyclicamidine, a chromium salt, and an organoaluminum compound. The presentdisclosure also relates to processes comprising a) contacting i)ethylene and ii) a catalyst system comprising (a) (i) an N²-phosphinylbicyclic amidine chromium salt complex or (ii) a chromium salt and anN²-phosphinyl bicyclic amidine and (b) an organoaluminum compound, andiii) optionally an organic reaction medium, and b) forming an oligomerproduct in a reaction zone. The N²-phosphinyl bicyclic amidine chromiumsalt complex, the chromium salt, the N²-phosphinyl bicyclic amidine, theorganoaluminum compound, and the optional organic reaction medium whichcan be utilized in the catalyst system and processes are independentlydescribed herein and can be utilized in any combination and withoutlimitation to describe the catalyst systems and processes of thisdisclosure.

Generally, the N²-phosphinyl bicyclic amidines and N²-phosphinylbicyclic amidine chromium salt complexes encompassed by this disclosurehave at least one N²-phosphinyl bicyclic amidine group. In an aspect,the N²-phosphinyl bicyclic amidines and N²-phosphinyl bicyclic amidinechromium salt complexes can comprise only one N²-phosphinyl bicyclicamidine group; or alternatively, can comprise only two N²-phosphinylbicyclic amidine groups. In an aspect, the N²-phosphinyl bicyclicamidines, regardless of the number of N²-phosphinyl bicyclic amidinegroups, or structure, can be non-metallic (i.e., a non-metallicN²-phosphinyl bicyclic amidine or a non-metallic compound having anN²-phosphinyl bicyclic amidine group).

In an aspect, the N²-phosphinyl bicyclic amidine can have Structure NPBAI or NPBA II. In an aspect, the N²-phosphinyl bicyclic amidine chromiumsalt complex can have Structure NPBACr I or NPBACr II.

Within the N²-phosphinyl bicyclic amidine having Structure NPBA I and/orNPBA II, R¹¹, R¹², R¹³, R₁₄, R¹⁵, R¹⁶, R¹⁷, R¹⁸, L¹, L², R⁴, and R⁵ areindependent elements of the N²-phosphinyl bicyclic amidine havingStructure NPBA I and/or NPBA II and are independently described herein.The independent descriptions of R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸,L¹, L², R⁴, and R⁵ can be utilized without limitation, and in anycombination, to describe the N²-phosphinyl bicyclic amidine havingStructure NPBA I and/or NPBA II which can be utilized in any aspectdescribed herein. Within the N²-phosphinyl bicyclic amidine chromiumsalt complex having Structure NPBACr I and/or NPBACr II, R¹¹, R¹², R¹³,R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, L¹, L², R⁴, and R⁵ of the N²-phosphinylbicyclic amidine and the chromium salt, CrX_(p), are independentelements of the N²-phosphinyl bicyclic amidine chromium salt complexeshaving Structure NPBACr I and/or NPBACr and are independently describedherein. The independent description of R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶,R¹⁷, R¹⁸, L¹, L², R⁴, R⁵ and CrX_(p) can be utilized without limitation,and in any combination, to describe the N²-phosphinyl bicyclic amidinechromium salt complex having Structure NPBACr I and/or NPBACr II whichcan be utilized in any aspect described herein.

Generally, R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ of theN²-phosphinyl bicyclic amidine structures and/or the N²-phosphinylbicyclic amidine chromium salt complex structures each independently canbe hydrogen or an organyl group; alternatively, hydrogen or an organylgroup consisting of inert functional groups; alternatively, a hydrogenor hydrocarbyl group; alternatively, an organyl group; alternatively, anorganyl group consisting of inert functional groups; alternatively, ahydrocarbyl group; or alternatively, hydrogen. In an aspect, the organylgroups which can be utilized as a non-hydrogen R¹¹, R¹², R¹³, R¹⁴, R¹⁵,R¹⁶, R¹⁷, and/or R¹⁸ can be a C₁ to C₂₀, a C₁ to C₁₅, a C₁ to C₁₀, or aC₁ to C₅ organyl group. In an aspect, the organyl group consisting ofinert functional groups which can be utilized as a non-hydrogen R¹¹,R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸ can be a C₁ to C₂₀, a C₁ toC₁₅, a C₁ to C₁₀, or a C₁ to C₅ organyl group consisting of inertfunctional groups. In an aspect, the hydrocarbyl group which can beutilized as a non-hydrogen R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸can be a C₁ to C₂₀, a C₁ to C₁₅, a C₁ to C₁₀, or a C₁ to C₅ hydrocarbylgroup.

In an aspect, each non-hydrogen R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷,and/or R¹⁸ of the N²-phosphinyl bicyclic amidines and/or theN²-phosphinyl bicyclic amidine chromium salt complexes independently canbe an alkyl group, a substituted alkyl group, a cycloalkyl group, asubstituted cycloalkyl group, an aryl group, a substituted aryl group,an aralkyl group, or a substituted aralkyl group; alternatively an alkylgroup or a substituted alkyl group; alternatively, a cycloalkyl group ora substituted cycloalkyl group; alternatively, an aryl group or asubstituted aryl group; alternatively, an aralkyl group or a substitutedaralkyl group; alternatively, an alkyl group, a cycloalkyl group, anaryl group, or an aralkyl group; alternatively, an alkyl group;alternatively, a substituted alkyl group, alternatively, a cycloalkylgroup; alternatively, a substituted cycloalkyl group; alternatively, anaryl group; alternatively, a substituted aryl group; alternatively, anaralkyl group; or alternatively, a substituted aralkyl group. In anyaspect disclosed herein, any R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/orR¹⁸ alkyl group independently can be a C₁ to C₂₀, a C₁ to C₁₀, or a C₁to C₅ alkyl group. In any aspect disclosed herein, any R¹¹, R¹², R¹³,R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸ substituted alkyl group independently canbe a C₁ to C₂₀, a C₁ to C₁₀, or a C₁ to C₅ substituted alkyl group. Inany aspect disclosed herein, any R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷,and/or R¹⁸ cycloalkyl group independently can be a C₄ to C₂₀, a C₄ toC₁₅, or a C₄ to C₁₀ cycloalkyl group. In any aspect disclosed herein,any R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸ substituted cycloalkylgroup independently can be a C₄ to C₂₀, a C₄ to C₁₅, or a C₄ to C₁₀substituted cycloalkyl group. In any aspect disclosed herein, any R¹¹,R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸ aryl group independently can bea C₆ to C₂₀, a C₆ to C₁₅, or a C₆ to C₁₀ aryl group. In any aspectdisclosed herein, any R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸substituted aryl group independently can be a C₆ to C₂₀, a C₆ to C₁₅, ora C₆ to C₁₀ substituted aryl group. In any aspect disclosed herein, anyR¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸ aralkyl groupindependently can be a C₇ to C₂₀, a C₇ to C₁₅, or a C₇ to C₁₀ aralkylgroup. In any aspect disclosed herein, any R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶,R¹⁷, and/or R¹⁸ substituted aralkyl group independently can be a C₇ toC₂₀, a C₇ to C₁₅, or a C₇ to C₁₀ substituted aralkyl group. Eachsubstituent of a substituted alkyl group (general or specific), asubstituted cycloalkyl group (general or specific), a substituted arylgroup (general or specific), and/or substituted aralkyl group (generalor specific) can be a halogen, a hydrocarbyl group, or a hydrocarboxygroup; alternatively, a halogen or a hydrocarbyl group; alternatively, ahalogen or a hydrocarboxy group; alternatively, a hydrocarbyl group or ahydrocarboxy group; alternatively, a halogen; alternatively, ahydrocarbyl group; or alternatively, a hydrocarboxy group. Substituenthalogens, substituent hydrocarbyl groups (general and specific), andsubstituent hydrocarboxy groups (general and specific) are independentlydisclosed herein. These substituent halogens, substituent hydrocarbylgroups, and substituent hydrocarboxy groups can be utilized withoutlimitation to further describe a substituted non-hydrogen R¹¹, R¹², R¹³,R¹⁴, R¹⁵, R¹⁶, R¹⁷ and/or R¹⁸.

In an aspect, when any of R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷ and/or R¹⁸of the N²-phosphinyl bicyclic amidine structures and the N²-phosphinylbicyclic amidine chromium salt complex structures are not hydrogen, eachnon-hydrogen R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸ of theN²-phosphinyl bicyclic amidines and/or the N²-phosphinyl bicyclicamidine chromium salt complexes independently can be a methyl group, anethyl group, a propyl group, a butyl group, a pentyl group, a hexylgroup, a heptyl group, or an octyl group; or alternatively, a methylgroup, an ethyl group, a n-propyl (1-propyl) group, an iso-propyl(2-propyl) group, a tert-butyl (2-methyl-2-propyl) group, or a neopentyl(2,2-dimethyl-1-propyl) group. In some aspects, the alkyl groups whichcan be utilized as R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and/or R¹⁸ can besubstituted. Each substituent of a substituted alkyl group (general orspecific) independently can be a halogen or a hydrocarboxy group;alternatively, a halogen; or alternatively, a hydrocarboxy group.Substituent halogens and substituent hydrocarboxy groups (general andspecific) are independently disclosed herein. These substituent halogensand substituent hydrocarboxy groups can be utilized without limitationto further describe a substituted alkyl group which can be utilized as anon-hydrogen R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷ and/or R¹⁸.

In an aspect, L¹ and L², of the N²-phosphinyl bicyclic amidines and theN²-phosphinyl bicyclic amidine chromium salt complexes having an L¹and/or L², independently can an organylene group; alternatively, anorganylene group consisting of inert functional groups; oralternatively, a hydrocarbylene group. The L¹ and/or L² organylenegroups independently can be a C₁ to C₂₀, a C₁ to C₁₅, a C₁ to C₁₀, or aC₁ to C₅ organylene group. The L¹ and/or L² organylene groups consistingof inert functional groups independently can be a C₁ to C₂₀, a C₁ toC₁₅, a C₁ to C₁₀, or a C₁ to C₅ organylene group consisting of inertfunctional groups. The L¹ and/or L² hydrocarbylene groups independentlycan be a C₁ to C₂₀, a C₁ to C₁₅, a C₁ to C₁₀, or a C₁ to C₅hydrocarbylene group.

In an aspect, L¹ and/or L² of the N²-phosphinyl bicyclic amidines andthe N²-phosphinyl bicyclic amidine chromium salt complexes having an L¹and/or L², independently can have any structure provided in Table 1. Insome aspects, L¹ and/or L² can have Structure 1L, Structure 2L,Structure 3L, Structure 4L or Structure 5L. In some aspects, L¹ and/orL² can have Structure 2L, Structure 3L, or Structure 4L; alternatively,Structure 5L or Structure 6L. In other aspects, L¹ and/or L² can haveStructure 1L; alternatively, Structure 2L; alternatively, Structure 3L;alternatively, Structure 4L; alternatively, Structure 5L; oralternatively Structure 6L.

TABLE 1 Structures for Linking Groups L¹ and/or L².—(CR^(L1)R^(L2))_(m)— —CR^(L1)R^(L2) _(m)— —CR^(L3)R^(L4)—CR^(L5)R^(L6)—Structure 1L Structure 2L Structure 3L—CR^(L3)R^(L4)—CR^(L7)R^(L8)—CR^(L5)R^(L6)— —CRL¹¹═CR^(L12)——CR^(L21)R^(L22)—CR²³═CR²⁴— Structure 4L Structure 5L Structure 6LWithin the structures of Table 1, the undesignated valences of L¹ and/orL² represent the points at which L¹ and/or L², when present in theN²-phosphinyl bicyclic amidines and/or the N²-phosphinyl bicyclicamidine chromium salt complexes, attach to the designated atoms of theN²-phosphinyl bicyclic amidine and/or the N²-phosphinyl bicyclic amidinechromium salt complex. In an aspect, m for the L¹ and/or L² linkinggroup having Structure 1L independently can be an integer ranging from 1to 5; alternatively, 1 to 3; alternatively, 1; alternatively, 2; oralternatively, 3. In an aspect, R^(L1) and R^(L2) of the linking grouphaving Structure 1L or Structure 2L, R^(L3), R^(L4), R^(L5), and R^(L6)of the linking group having Structure 3L, R^(L3), R^(L4), R^(L5),R^(L6), R^(L7), and R^(L8) of the linking group having Structure 4L,R^(L11) and R^(L12) of the linking group having Structure 5L, andR^(L21), R^(L22), R^(L23), and R^(L24) of the linking group havingStructure 6L independently can be a hydrogen or a non-hydrogensubstituent group; or alternatively, hydrogen. Non-hydrogen substituentgroups (general and specific) are independently disclosed herein and canbe utilized without limitation to further describe the linking grouphaving Structure 1L, Structure 2L, Structure 3L, Structure 4L, Structure5L, and/or Structure 6L. In an aspect, L¹ and/or L² independently can bea methylene group (—CH₂—), an eth-1,2-ylene group (—CH₂CH₂—), anethen-1,2-ylene group (—CH═CH—), a prop-1,3-ylene group (—CH₂CH₂CH₂—), aprop-1,2-ylene group (—CH(CH₃)CH₂—), a propen-1,3-ylene group(—CH₂CH═CH—), a propen-1,2-ylene group (—CH═CH(CH₃)—), a but-1,4-ylenegroup (—CH₂CH₂CH₂CH₂—), a but-1,3-ylene group (—CH₂CH₂CH(CH₃)—), a2-methylprop-1,3-ylene group (—CH₂CH(CH₃)CH₂—), a 2-methylprop-1,2-ylenegroup (—C(CH₃)₂CH₂—), a but-1,2-en-1,4-ylene group (—CH₂CH₂CH═CH—), abut-1,2-en-1,3-ylene group (—CH(CH₃)CH═CH—), a but-2,3-en-1,4-ylenegroup (—CH₂CH═CHCH₂—), or a 2-methylpropen-1,3-ylene group(—CH₂C(CH₃)=CH—). In some non-limiting aspects, L′ and/or L² be amethylene group (—CH₂—), an eth-1,2-ylene group (—CH₂CH₂—), anethen-1,2-ylene group (—CH═CH—), a prop-1,3-ylene group (—CH₂CH₂CH₂—),—), a prop-1,2-ylene group (—CH(CH₃)CH₂—), a propen-1,3-ylene group(—CH₂CH═CH—), a propen-1,2-ylene group (—CH═CH(CH₃)—), a but-1,3-ylenegroup (—CH₂CH₂CH(CH₃)—), a 2-methylprop-1,3-ylene group(—CH₂CH(CH₃)CH₂—), a 2-methylprop-1,2-ylene group (—C(CH₃)₂CH₂—), or a2-methylpropen-1,3-ylene group (—CH₂C(CH₃)=CH—); alternatively, amethylene group (—CH₂—), an eth-1,2-ylene group (—CH₂CH₂—), aprop-1,3-ylene group (—CH₂CH₂CH₂—), a prop-1,2-ylene group(—CH(CH₃)CH₂—), a but-1,3-ylene group (—CH₂CH₂CH(CH₃)—), a2-methylprop-1,3-ylene group (—CH₂CH(CH₃)CH₂—), or a2-methylprop-1,2-ylene group (—C(CH₃)₂CH₂—); alternatively, a methylenegroup (—CH₂—), an eth-1,2-ylene group (—CH₂CH₂—), or a prop-1,3-ylenegroup (—CH₂CH₂CH₂—); alternatively, a methylene group (—CH₂—), or aneth-1,2-ylene group (—CH₂CH₂—); alternatively, a methylene group(—CH₂—); alternatively, an eth-1,2-ylene group (—CH₂CH₂—); oralternatively, a prop-1,3-ylene group (—CH₂CH₂CH₂—). The specific L¹sand/or L²s are given their proper names. However, these proper names arenot intended to imply which atoms of the N²-phosphinyl bicyclic amidinesand/or the N²-phosphinyl bicyclic amidine chromium salt complexes theundesignated valencies are attached to. The undesignated valencies canbe attached to either of the two N²-phosphinyl bicyclic amidines or theN²-phosphinyl bicyclic amidine chromium salt complexes designated atomsas long as it provides a proper N²-phosphinyl bicyclic amidine or theN²-phosphinyl bicyclic amidine chromium salt complex unless otherwisespecified.

Generally, R⁴ and/or R⁵ of the N²-phosphinyl bicyclic amidines and/orthe N²-phosphinyl bicyclic amidine chromium salt complexes independentlycan be an organyl group; alternatively, an organyl group consisting ofinert functional groups; or alternatively, a hydrocarbyl group. In anaspect, the R⁴ and/or R⁵ organyl groups can be a C₁ to C₂₀, a C₁ to C₁₅,a C₁ to C₁₀, or a C₁ to C₅ organyl group. In an aspect, the R⁴ and/or R⁵organyl groups consisting of inert functional groups can be a C₁ to C₂₀,a C₁ to C₁₅, a C₁ to C₁₀, or a C₁ to C₅ organyl group consisting ofinert functional groups. In an aspect, the R⁴ and/or R⁵ hydrocarbylgroups can be a, a C₁ to C₂₀, a C₁ to C₁₅, a C₁ to C₁₀, or a C₁ to C₅hydrocarbyl group. In an aspect, R⁴ and/or R⁵ of the N²-phosphinylbicyclic amidines and/or the N²-phosphinyl bicyclic amidine chromiumsalt complexes independently can be an alkyl group, a substituted alkylgroup, a cycloalkyl group, a substituted cycloalkyl group, an arylgroup, a substituted aryl group, an aralkyl group, or a substitutedaralkyl group; alternatively, an alkyl group or a substituted alkylgroup; alternatively, a cycloalkyl group or a substituted cycloalkylgroup; alternatively, an aryl group or a substituted aryl group;alternatively, an aralkyl group or a substituted aralkyl group;alternatively, an alkyl group, a cycloalkyl group, an aryl group, or anaralkyl group; alternatively, an alkyl group; alternatively, asubstituted alkyl group, alternatively, a cycloalkyl group;alternatively, a substituted cycloalkyl group; alternatively, an arylgroup; alternatively, a substituted aryl group; alternatively, anaralkyl group; or alternatively, a substituted aralkyl group.

In any aspect disclosed herein, the R⁴ and/or R⁵ alkyl groupsindependently can be a C₁ to C₂₀, a C₁ to C₁₀, or a C₁ to C₅ alkylgroup. In any aspect disclosed herein, the R⁴ and/or R⁵ substitutedalkyl groups independently can be a C₁ to C₂₀, a C₁ to C₁₀, or C₁ to C₅substituted alkyl group. In any aspect disclosed herein, the R⁴ and/orR⁵ cycloalkyl groups independently can be a C₄ to C₂₀, a C₄ to C₁₅, or aC₄ to C₁₀ cycloalkyl group. In any aspect disclosed herein, the R⁴and/or R⁵ substituted cycloalkyl groups independently can be a C₄ toC₂₀, a C₄ to C₁₅, or a C₄ to C₁₀ substituted cycloalkyl group. In anyaspect disclosed herein, the R⁴ and/or R⁵ aryl groups independently canbe a C₆ to C₂₀, a C₆ to C₁₅, or a C₆ to CH) aryl group. In any aspectdisclosed herein, the R⁴ and/or R⁵ substituted aryl group independentlycan be a C₆ to C₂₀, a C₆ to C₁₅, or a C₆ to C₁₀ substituted aryl group.In any aspect disclosed herein, the R⁴ and/or R⁵ aralkyl groupsindependently can be a C₇ to C₂₀, a C₇ to C₁₅, or a C₇ to C₁₀ aralkylgroup. In any aspect disclosed herein, the R⁴ and/or R⁵ substituted arylgroups independently can be a C₇ to C₂₀, a C₇ to C₁₅, or a C₇ to C₁₀substituted aralkyl group. Each substituent of a substituted alkyl group(general or specific), a substituted cycloalkyl group (general orspecific), a substituted aryl group (general or specific), and/orsubstituted aralkyl group (general or specific) can be a halogen, ahydrocarbyl group, or a hydrocarboxy group; alternatively, a halogen ora hydrocarbyl group; alternatively, a halogen or a hydrocarboxy group;alternatively, a hydrocarbyl group or a hydrocarboxy group;alternatively, a halogen; alternatively, a hydrocarbyl group; oralternatively, a hydrocarboxy group. Substituent halogens, substituenthydrocarbyl groups (general and specific), and substituent hydrocarboxygroups (general and specific) are independently disclosed herein. Thesesubstituent halogens, substituent hydrocarbyl groups, and substituenthydrocarboxy groups can be utilized without limitation to furtherdescribe R⁴ and/or R⁵.

In an aspect, R⁴ and R⁵ independently can be a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, or an octyl group; or alternatively, a methyl group, anethyl group, an n-propyl (1-propyl) group, an iso-propyl (2-propyl)group, a 2-methyl-1-propyl group, a tert-butyl (2-methyl-2-propyl)group, or a neopentyl (2,2-dimethyl-1-propyl) group. In some aspects,the alkyl groups which can be utilized as R⁴ and/or R⁵ can besubstituted. Each substituent of a substituted alkyl group independentlycan be a halogen or a hydrocarboxy group; alternatively, a halogen; oralternatively, a hydrocarboxy group. Substituent halogens andsubstituent hydrocarboxy (general and specific) groups are independentlydisclosed herein. These substituent halogens and substituenthydrocarboxy groups can be utilized without limitation to furtherdescribe a substituted alkyl group which can be utilized as R⁴ and/orR⁵.

In an aspect, R⁴ and R⁵ independently can be a cyclopentyl group, asubstituted cyclopentyl group, a cyclohexyl group, or a substitutedcyclohexyl group; alternatively, a cyclopentyl group or a substitutedcyclopentyl group; or alternatively, a cyclohexyl group or a substitutedcyclohexyl group. In an aspect, the substituted cycloalkyl group, whichcan be utilized for R⁴ and/or R⁵, can be a 2-substituted cyclohexylgroup, a 2,6-disubstituted cyclohexyl group, a 2-substituted cyclopentylgroup, or a 2,5-disubstituted cyclopentyl group; alternatively, a2-substituted cyclohexyl group or a 2,6-disubstituted cyclohexyl group;alternatively, a 2-substituted cyclopentyl group or a 2,5-disubstitutedcyclopentyl group; alternatively, a 2-substituted cyclohexyl group or a2-substituted cyclopentyl group; or alternatively, a 2,6-disubstitutedcyclohexyl group or a 2,5-disubstituted cyclopentyl group. When thesubstituted cycloalkyl group (general or specific) has more the onesubstituent, the substituents can be the same or different;alternatively, the same; or alternatively, different. Each substituentof a cycloalkyl group (general or specific) having a specified number ofring carbon atoms independently can be a halogen, a hydrocarbyl group,or a hydrocarboxy group; alternatively, a halogen or a hydrocarbylgroup; alternatively, a halogen or a hydrocarboxy group; alternatively,a hydrocarbyl group or a hydrocarboxy group; alternatively, a halogen,alternatively, a hydrocarbyl group; or alternatively, a hydrocarboxygroup. Substituent halogens, substituent hydrocarbyl groups (general andspecific), and substituent hydrocarboxy groups (general and specific)are independently disclosed herein. These substituent halogens,substituent hydrocarbyl groups, and substituent hydrocarboxy groups canbe utilized without limitation to further describe a substitutedcycloalkyl group (general or specific) which can be utilized as R⁴and/or R⁵.

In a non-limiting aspect, R⁴ and R⁵ independently can be a cyclohexylgroup, a 2-alkylcyclohexyl group, or a 2,6-dialkylcyclohexyl group; oralternatively, a cyclopentyl group, a 2-alkylcyclopentyl group, or a2,5-dialkylcyclopentyl group. Alkyl substituent groups (general andspecific) are independently described herein and these alkyl substituentgroups can be utilized, without limitation, to further describedalkylcyclohexyl groups (general or specific), dialkylcyclohexyl groups(general or specific), alkylcyclopentyl groups (general or specific),and/or dialkylcyclopentyl groups (general or specific) which can beutilized as R⁴ and/or R⁵. Generally, the alkyl substituents of adisubstituted cyclohexyl or cyclopentyl group can be the same; oralternatively, the alkyl substituents of a dialkyl cyclohexyl orcyclopentyl group can be different. In some non-limiting aspects, R⁴ andR⁵ independently can be a 2-methylcyclohexyl group, a 2-ethylcyclohexylgroup, a 2-isopropylcyclohexyl group, a 2-tert-butylcyclohexyl group, a2,6-dimethylcyclohexyl group, a 2,6-diethylcyclohexyl group, a2,6-diisopropylcyclohexyl group, or a 2,6-di-tert-butylcyclohexyl group.In other non-limiting aspects, R⁴ and R⁵ independently can be, a2-methylcyclohexyl group, a 2-ethylcyclohexyl group, a2-isopropylcyclohexyl group, or a 2-tert-butylcyclohexyl group; oralternatively, a 2,6-dimethylcyclohexyl group, a 2,6-diethylcyclohexylgroup, a 2,6-diisopropylcyclohexyl group, or a2,6-di-tert-butylcyclohexyl group.

In an aspect, R⁴ and R⁵ independently can be a phenyl group, asubstituted phenyl group; alternatively, a phenyl group; oralternatively, a substituted phenyl group. In an aspect, the substitutedphenyl group, which can be utilized for R⁴ and/or R⁵, can be a2-substituted phenyl group, a 3-substituted phenyl group, a4-substituted phenyl group, a 2,4-disubstituted phenyl group, a2,6-disubstituted phenyl group, a 3,5-disubstituted phenyl group, or a2,4,6-trisubstituted phenyl group; alternatively, a 2-substituted phenylgroup, a 4-substituted phenyl group, a 2,4-disubstituted phenyl group,or a 2,6-disubstituted phenyl group; alternatively, a 3-substitutedphenyl group or a 3,5-disubstituted phenyl group; alternatively, a2-substituted phenyl group or a 4-substituted phenyl group;alternatively, a 2,4-disubstituted phenyl group or a 2,6-disubstitutedphenyl group; or alternatively, a 2,4,6-trisubstituted phenyl group.When the substituted phenyl group (general or specific) has more the onesubstituent, the substituents can be the same or different;alternatively, all the substituents of a multi-substituted phenyl groupcan be the same; or alternatively, all the substituents of amulti-substituted phenyl group different. Each substituent of asubstituted phenyl group (general or specific) independently can be ahalogen, a hydrocarbyl group, or a hydrocarboxy group; alternatively, ahalogen or a hydrocarbyl group; alternatively, a halogen or ahydrocarboxy group; alternatively, a hydrocarbyl group or a hydrocarboxygroup; alternatively, a halogen, alternatively, a hydrocarbyl group; oralternatively, a hydrocarboxy group. Substituent halogens, substituenthydrocarbyl groups (general and specific), and substituent hydrocarboxygroups (general and specific) are independently disclosed herein. Thesesubstituent halogens, substituent hydrocarbyl groups, and substituenthydrocarboxy groups can be utilized without limitation to furtherdescribe a substituted phenyl group (general or specific) which can beutilized as R⁴ and/or R⁵.

In a non-limiting aspect, R⁴ and R⁵ independently can be a phenyl group,a 2-alkylphenyl group, a 3-alkylphenyl group, a 4-alkylphenyl group, a2,4-dialkylphenyl group a 2,6-dialkylphenyl group, a 3,5-dialkylphenylgroup, or a 2,4,6-trialkylphenyl group; alternatively, a 2-alkylphenylgroup, a 4-alkylphenyl group, a 2,4-dialkylphenyl group, a2,6-dialkylphenyl group, or a 2,4,6-trialkylphenyl group; alternatively,a 2-alkylphenyl group or a 4-alkylphenyl group; alternatively, a2,4-dialkylphenyl group or a 2,6-dialkylphenyl group; alternatively, a3-alkylphenyl group or a 3,5-dialkylphenyl group; alternatively, a2-alkylphenyl group or a 2,6-dialkylphenyl group; or alternatively, a2,4,6-trialkylphenyl group. Alkyl substituent groups (general andspecific) are independently described herein and these alkyl substituentgroups can be utilized, without limitation, to further describe anyalkyl substituted phenyl group which can be utilized as R⁴ and/or R⁵.Generally, the alkyl substituents of a dialkylphenyl group (general orspecific) or a trialkylphenyl group (general or specific) can be thesame; or alternatively, the alkyl substituents of a dialkylphenyl group(general or specific) or a trialkyl phenyl group (general or specific)can be different. In some non-limiting aspects, R⁴ and R⁵ independentlycan be a phenyl group, a 2-methylphenyl group, a 2-ethylphenyl group, a2-n-propylphenyl group, a 2-isopropylphenyl group, a 2-tert-butylphenylgroup, a 2,6-dimethylphenyl group, a 2,6-diethylphenyl group, a2,6-di-n-propylphenyl group, a 2,6-diisopropylphenyl group, a2,6-di-tert-butylphenyl group, a 2-isopropyl-6-methylphenyl group, or a2,4,6-trimethylphenyl group; alternatively, phenyl group, a2-methylphenyl group, a 2-ethylphenyl group, a 2-n-propylphenyl group, a2-isopropylphenyl group, or a 2-tert-butylphenyl group; alternatively, aphenyl group, a 2,6-dimethylphenyl group, a 2,6-diethylphenyl group, a2,6-di-n-propylphenyl group, a 2,6-diisopropylphenyl group, a2,6-di-tert-butylphenyl group, a 2-isopropyl-6-methylphenyl group, or a2,4,6-trimethylphenyl group.

In a non-limiting aspect, R⁴ and R⁵ can be a phenyl group, a2-alkoxyphenyl group, or a 4-alkoxyphenyl group. In some non-limitingaspects, R⁴ and/or R⁵ can be a phenyl group, a 2-methoxyphenyl group, a2-ethoxyphenyl group, a 2-isopropoxyphenyl group, a 2-tert-butoxyphenylgroup, a 4-methoxyphenyl group, a 4-ethoxyphenyl group, a4-isopropoxyphenyl group, or a 4-tert-butoxyphenyl group; alternatively,a 2-methoxyphenyl group, a 2-ethoxyphenyl group, a 2-isopropoxyphenylgroup, or a 2-tert-butoxyphenyl group; or alternatively, a4-methoxyphenyl group, a 4-ethoxyphenyl group, a 4-isopropoxyphenylgroup, or a 4-tert-butoxyphenyl group. In a non-limiting aspect, R⁴ andR⁵ independently can be a phenyl group, a 2-halophenyl group, a4-halophenyl group, or a 2,6-dihalophenylgroup. Generally, the halidesof a dihalophenyl group can be the same; or alternatively, the halidesof a dihalophenyl group can be different. In some aspects, R⁴ and R⁵independently can be a phenyl group, a 2-fluorophenyl group, a4-fluorophenyl group, or a 2,6-difluorophenyl group.

In an aspect, R⁴ and R⁵ independently can be a benzyl group or asubstituted benzyl group; alternatively, a benzyl group; oralternatively, a substituted benzyl group. Each substituent of asubstituted benzyl group independently can be a halogen, a hydrocarbylgroup, or a hydrocarboxy group; alternatively, a halogen or ahydrocarbyl group; alternatively, a halogen or a hydrocarboxy group;alternatively, a hydrocarbyl group or a hydrocarboxy group;alternatively, a halogen, alternatively, a hydrocarbyl group; oralternatively, a hydrocarboxy group. Substituent halogens, substituenthydrocarbyl groups (general and specific), and substituent hydrocarboxygroups (general and specific) are independently disclosed herein. Thesesubstituent halogens, substituent hydrocarbyl groups, and substituenthydrocarboxy groups can be utilized without limitation to furtherdescribe a substituted benzyl which can be utilized as R⁴ and/or R⁵.

In further aspects, R⁴ and R⁵ can be joined to form a ring or a ringsystem containing the phosphorus atom. The joining of R⁴ and R⁵ can bedesignated as L⁴⁵ and can be an organylene group; alternatively, anorganylene group consisting of inert functional groups; alternatively, ahydrocarbylene group; or alternatively, an alkylene group. In an aspect,the L⁴⁵ organylene group, when present, can be a C₄ to C₃₀, a C₄ to C₂₀,a C₄ to C₁₅, or a C₄ to C₁₀ organylene group. In an aspect, the L⁴⁵organylene group consisting of inert functional groups, when present,can be a C₄ to C₃₀, a C₄ to C₂₀, a C₄ to C₁₅, or a C₄ to C₁₀ organylenegroup consisting of inert functional groups. In an aspect, the L⁴⁵hydrocarbyl group, when present, independently can be a C₄ to C₃₀, a C₄to C₂₀, a C₄ to C₁₅, or a C₄ to C₁₀ hydrocarbylene group. In a furtheraspect, the L⁴⁵ alkylene group, when present, independently can be a C₄to C₃₀, a C₄ to C₂₀, a C₄ to C₁₅, or a C₄ to C₁₀ alkylene group. In anaspect, L⁴⁵ can be a but-1,4-ylene group, a 1,4-diphenylbut-1,4-ylenegroup, a 1,4-di(2-methylphenyl)but-1,4-ylene group,1,4-di(4-methylphenyl)but-1,4-ylene group,1,4-di(4-t-butylphenyl)but-1,4-ylene group, a1,4-di(3,5-dimethylphenyl)but-1,4-ylene group, a pent-1,4-ylene group, a1-phenylpenta-1,4-ylene group, a 4-phenylpenta-1,4-ylene group, ahex-2,5-ylene group, a 2,2′-biphenylene group, a2,2′-(methandiyOdipheylene group, or a 2,2′-(1,2-ethandiyl)diphenylenegroup.

Various aspects described herein refer to non-hydrogen substituents suchas halogen (or halo, halide), hydrocarbyl, hydrocarboxy, alkyl, and/oralkoxy substituents. In an aspect, each non-hydrogen substituent of anyaspect calling for a substituent can be a halogen, a hydrocarbyl group,or a hydrocarboxy group; alternatively, a halogen or a hydrocarbylgroup; alternatively, a halogen or a hydrocarboxy group; alternatively,a hydrocarbyl group or a hydrocarboxy group; alternatively, a halogen;alternatively, a hydrocarbyl group; or alternatively, a hydrocarboxygroup. Each hydrocarbyl substituent independently can be a C₁ to C₁₀hydrocarbyl group; or alternatively, a C₁ to C₅ hydrocarbyl group. Eachhydrocarboxy substituent independently can be a C₁ to C₁₀ hydrocarboxygroup; or alternatively, a C₁ to C₅ hydrocarboxy group. Each halidesubstituent independently can be a fluoride, chloride, bromide, oriodide; alternatively, a fluoride or chloride; alternatively, afluoride; alternatively, a chloride; alternatively, a bromide; oralternatively, an iodide.

In an aspect, any hydrocarbyl substituent independently can be an alkylgroup, an aryl group, or an aralkyl group; alternatively, an alkylgroup; alternatively, an aryl group; or alternatively, an aralkyl group.In an aspect, any alkyl substituent independently can be a methyl group,an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,a sec-butyl group, an isobutyl group, a tert-butyl group, an n-pentylgroup, a 2-pentyl group, a 3-pentyl group, a 2-methyl-1-butyl group, atert-pentyl group, a 3-methyl-1-butyl group, a 3-methyl-2-butyl group,or a neo-pentyl group; alternatively, a methyl group, an ethyl group, anisopropyl group, a tert-butyl group, or a neo-pentyl group;alternatively, a methyl group; alternatively, an ethyl group;alternatively, an isopropyl group; alternatively, a tert-butyl group; oralternatively, a neo-pentyl group. In an aspect, any aryl substituentindependently can be phenyl group, a tolyl group, a xylyl group, or a2,4,6-trimethylphenyl group; alternatively, a phenyl group;alternatively, a tolyl group, alternatively, a xylyl group; oralternatively, a 2,4,6-trimethylphenyl group. In an aspect, any aralkylsubstituent independently can be benzyl group or an ethylphenyl group(2-phenyleth-1-yl or 1-phenyleth-1-yl); alternatively, a benzyl group;alternatively, an ethylphenyl group; alternatively, a 2-phenyleth-1-ylgroup; or alternatively, a 1-phenyleth-1-yl group.

In an aspect, any hydrocarboxy substituent independently can be analkoxy group, an aryloxy group, or an aralkoxy group; alternatively, analkoxy group; alternatively, an aryloxy group, or an aralkoxy group. Inan aspect, any alkoxy substituent independently can be a methoxy group,an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxygroup, a sec-butoxy group, an isobutoxy group, a tert-butoxy group, ann-pentoxy group, a 2-pentoxy group, a 3-pentoxy group, a2-methyl-1-butoxy group, a tert-pentoxy group, a 3-methyl-1-butoxygroup, a 3-methyl-2-butoxy group, or a neo-pentoxy group; alternatively,a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxygroup, or a neo-pentoxy group; alternatively, a methoxy group;alternatively, an ethoxy group; alternatively, an isopropoxy group;alternatively, a tert-butoxy group; or alternatively, a neo-pentoxygroup. In an aspect, any aryloxy substituent independently can bephenoxy group, a toloxy group, a xyloxy group, or a2,4,6-trimethylphenoxy group; alternatively, a phenoxy group;alternatively, a toloxy group, alternatively, a xyloxy group; oralternatively, a 2,4,6-trimethylphenoxy group. In an aspect, anyaralkoxy substituent independently can be benzoxy group.

Various aspects disclosed herein can utilize a chromium salt or anN²-phosphinyl bicyclic amidine chromium salt complex. Generally, thechromium salt and/or the chromium salt of the N²-phosphinyl bicyclicamidine chromium salt complex can have the formula CrX_(p) where Xrepresents a monoanionic ligand and p represents the number ofmonoanionic ligands (and the oxidation state of the chromium in thechromium compound). The monoanionic ligand (X) and p are independentelements of the chromium salt and the chromium salt portion of theN²-phosphinyl bicyclic amidine chromium salt complex and areindependently described herein. These independent descriptions of themonoanionic ligand (X) and p can be utilized without limitation, and inany combination, to further describe the chromium salt and/or thechromium salt of the N²-phosphinyl bicyclic amidine chromium saltcomplex which can be utilized in various aspects described herein.

Generally, the chromium atom of the chromium salt (CrX_(p)) or thechromium salt of the N²-phosphinyl bicyclic amidine chromium saltcomplex can have any positive oxidation state available to a chromiumatom. In an aspect, the chromium atom can have an oxidation state offrom +2 to +6; alternatively, from +2 to +4; or alternatively, from +2to +3. In some aspects, the chromium atom of the chromium compound(CrX_(p)) can have an oxidation state of +1; alternatively, +2;alternatively, +3; or alternatively, +4.

The monoanion, X, of the chromium salt and/or the chromium salt of theN²-phosphinyl bicyclic amidine chromium salt complex can be anymonoanion. In an aspect, the monoanion (X) can be a halide, acarboxylate, a β-diketonate, a hydrocarboxide, a nitrate, or a chlorate.In some aspects, the monoanion (X) can be a halide, a carboxylate, aβ-diketonate, or a hydrocarboxide. In any aspect, the hydrocarboxide canbe an alkoxide, an aryloxide, or an aralkoxide. Generally,hydrocarboxide (and subdivisions of hydrocarboxide) are the anionanalogues of the hydrocarboxy group. In other aspects, the monoanion (X)can be a halide, a carboxylate, a β-diketonate, or an alkoxide; oralternatively, a halide or a β-diketonate. In other aspects, themonoanion (X) can be a halide; alternatively, a carboxylate;alternatively, a β-diketonate; alternatively, a hydrocarboxide;alternatively, an alkoxide; or alternatively, an aryloxide. In anaspect, the number of monoanions can be from 2 to 6; alternatively, from2 to 4; alternatively, from 2 to 3; alternatively, 1; alternatively, 2;alternatively, 3; or alternatively, 4.

Generally, each halide of the chromium salt (CrX_(p)) or the chromiumsalt of the N²-phosphinyl bicyclic amidine chromium salt complexindependently can be fluorine, chlorine, bromine, or iodine; oralternatively, chlorine, bromine, or iodine. In an aspect, each halidemonoanion of the chromium compound can be chlorine; alternatively,bromine; or alternatively, iodine.

Generally, each carboxylate of the chromium salt (CrX_(p)) or thechromium salt of the N²-phosphinyl bicyclic amidine chromium saltcomplex independently can be a C₁ to C₂₀ or C₁ to C₁₀ carboxylate. In anaspect, each carboxylate independently can be acetate, a propionate, abutyrate, a pentanoate, a hexanoate, a heptanoate, an octanoate, anonanoate, a decanoate, an undecanoate, or a dodecanoate; oralternatively, a pentanoate, a hexanoate, a heptanoate, an octanoate, anonanoate, a decanoate, an undecanoate, or a dodecanoate. In someaspects, each carboxylate independently can be acetate, propionate,n-butyrate, valerate (n-pentanoate), neo-pentanoate, capronate(n-hexanoate), n-heptanoate, caprylate (n-octanoate), 2-ethylhexanoate,n-nonanoate, caprate (n-decanoate), n-undecanoate, or laurate(n-dodecanoate); alternatively, valerate (n-pentanoate), neo-pentanoate,capronate (n-hexanoate), n-heptanoate, caprylate (n-octanoate),2-ethylhexanoate, n-nonanoate, caprate (n-decanoate), n-undecanoate, orlaurate (n-dodecanoate); alternatively, capronate (n-hexanoate);alternatively, n-heptanoate; alternatively, caprylate (n-octanoate); oralternatively, 2-ethylhexanoate. In some aspects, each carboxylate canbe triflate (trifluoroacetate).

Generally, each β-diketonate of the chromium salt (CrX_(p)) or thechromium salt of the N²-phosphinyl bicyclic amidine chromium saltcomplex independently can be a C₁ to C₂₀ or C₁ to C₁₀ diketonate. In anaspect, each β-diketonate independently can be acetylacetonate (i.e.,2,4-pentanedionate), hexafluoroacetylacetonate (i.e., 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate), or benzoylacetonate);alternatively, acetylacetonate; alternatively,hexafluoroacetylacetonate; or alternatively, benzoylacetonate.

Generally, each hydrocarboxide of the chromium salt (CrX_(p)) or thechromium salt of the N²-phosphinyl bicyclic amidine chromium saltcomplex independently can be a C₁ to C₂₀ or C₁ to C₁₀ hydrocarboxide. Inan aspect, each hydrocarboxide independently can be a C₁ to C₂₀ or C₁ toC₁₀ alkoxide; or alternatively, a C₆ to C₂₀ or C₆ to C₁₀ aryloxide. Inan aspect, each alkoxide independently can be methoxide, ethoxide, apropoxide, or a butoxide; alternatively, methoxide, ethoxide,isopropoxide, or tert-butoxide; alternatively, methoxide; alternatively,an ethoxide; alternatively, an iso-propoxide; or alternatively, atert-butoxide. In an aspect, the aryloxide can be phenoxide.

In some non-limiting aspects, the chromium salt (CrX_(p)) or thechromium salt of the N²-phosphinyl bicyclic amidine chromium saltcomplex can comprise, can consist essentially of, or consist of, achromium(II) halide, a chromium(II) carboxylate, or a chromium(II)β-diketonate; or alternatively, a chromium(III) halide, a chromium(III)carboxylate, or a chromium(III) β-diketonate. In other non-limitingaspects, the chromium salt (CrX_(p)) or the chromium salt of theN²-phosphinyl bicyclic amidine chromium salt complex can comprise, canconsist essentially of, or consist of, a chromium(II) halide;alternatively, a chromium(III) halide; alternatively, a chromium (II)carboxylate; alternatively, a chromium(III) carboxylate; alternatively,a chromium(II) β-diketonate; or alternatively, a chromium(III)β-diketonate. Halides, carboxylates, β-diketonates are independentlydescribed herein and these halides, carboxylates, β-diketonate and theseindependently described halides, carboxylates, β-diketonates can beutilized without limitation and in any combination to further describedthe chromium salt (CrX_(p)) or the chromium salt of the N²-phosphinylbicyclic amidine chromium salt complex. In further non-limiting aspects,the chromium salt (CrX_(p)) or the chromium salt of the N²-phosphinylbicyclic amidine chromium salt complex can comprise, can consistessentially of, or consist of, chromium(II) chloride, chromium(III)chloride, chromium(II) fluoride, chromium(III) fluoride, chromium(II)bromide, chromium(III) bromide, chromium(II) iodide, chromium(III)iodide, chromium(II) acetate, chromium(III) acetate, chromium(II)2-ethylhexanoate, chromium(III) 2-ethylhexanoate, chromium(II) triflate,chromium(III) triflate, chromium(II) nitrate, chromium(III) nitrate,chromium(II) acetylacetonate, chromium(III) acetylacetonate,chromium(II) hexafluoracetylacetonate, chromium(III)hexafluoracetylacetonate, chromium(III) benzoylacetonate, orchromium(III) benzoylacetonate; alternatively, chromium(III) chloride,chromium(III) fluoride, chromium(III) bromide, chromium(III) iodide,chromium(III) chloride (THF) complex, chromium(III) acetate,chromium(III) 2-ethylhexanoate, chromium(III) triflate, chromium(III)nitrate, chromium(III) acetylacetonate, chromium(III)hexafluoracetylacetonate, or chromium(III) benzoylacetonate;alternatively, chromium(III) chloride, or chromium(III) acetylacetonate;alternatively, chromium(III) chloride; or alternatively, chromium(III)acetylacetonate.

In an aspect, the N²-phosphinyl bicyclic amidine can have Structure NPBA1, NPBA 2, NPBA 3, NPBA 4, or NPBA 5; alternatively, Structure NPBA 1,NPBA 2, or NPBA 3; alternatively, Structure NPBA 1; alternatively,Structure NPBA 2; alternatively, Structure NPBA 3; alternatively,Structure NPBA 4; or alternatively NPBA 5.

In an aspect, the N²-phosphinyl bicyclic amidine chromium salt complexcan have Structure NPBACr 1, NPBACr 2, NPBACr 3, NPBACr 4, or NPBACr 5;alternatively, Structure NPBACr 1, NPBACr 2, or NPBACr 3; alternatively,Structure NPBACr 1; alternatively, Structure NPBACr 2; alternatively,Structure NPBACr 3; alternatively, Structure NPBACr 4; or alternativelyNPBACr 5.

While not identified for the chromium salts and shown in theN²-phosphinyl bicyclic amidine chromium salt complex structures providedherein, one of ordinary skill in the art will recognize that a neutralligand, Q, can be associated with the chromium salts the N²-phosphinylbicyclic amidine chromium salt complexes described/depicted herein.Additionally, it should be understood that while the chromium salts andthe N²-phosphinyl bicyclic amidine chromium salt complexesdescribed/depicted/provided herein do not formally show the presence ofa neutral ligand, the chromium salts and/or the N²-phosphinyl bicyclicamidine chromium salt complexes having neural ligands (e.g., nitrilesand ethers, among others) are implicitly and fully contemplated aspotential the chromium salts and/or the N²-phosphinyl bicyclic amidinechromium salt complexes that can be utilized in the catalyst system usedin aspects of the herein described inventions.

Generally, the neutral ligand of any chromium salt and/or N²-phosphinylbicyclic amidine chromium salt complex, when present, independently canbe any neutral ligand that forms an isolatable compound with thechromium salt and/or N²-phosphinyl bicyclic amidine chromium saltcomplex. In an aspect, each neutral ligand independently can be anitrile or an ether; alternatively, a nitrile; or alternatively, anether. The number of neutral ligands, q, can be any number that forms anisolatable compound with the chromium salt and/or N²-phosphinyl bicyclicamidine chromium salt complex. In an aspect, the number of neutralligands can be from 0 to 6; alternatively, 0 to 3; alternatively, 0;alternatively, 1; alternatively, 2; alternatively, 3; or alternatively,4.

Generally, each nitrile ligand independently can be a C₂ to C₂₀, or C₂to C₁₀ nitrile. In an aspect, each nitrile ligand independently can be aC₂ to C₂₀ aliphatic nitrile, a C₇ to C₂₀ aromatic nitrile, a C₈ to C₂₀aralkane nitrile, or any combination thereof; alternatively, a C₂ to C₂₀aliphatic nitrile; alternatively, a C₇ to C₂₀ aromatic nitrile; oralternatively, a C₈ to C₂₀ aralkane nitrile. In some aspects, eachnitrile ligand independently can be a C₂ to C₁₀ aliphatic nitrile, a C₇to C₁₀ aromatic nitrile, a C₈ to C₁₀ aralkane nitrile, or anycombination thereof; alternatively, a C₁ to C₁₀ aliphatic nitrile;alternatively, a C₇ to C₁₀ aromatic nitrile; or alternatively, a C₈ toC₁₀ aralkane nitrile. In an aspect, each aliphatic nitrile independentlycan be acetonitrile, propionitrile, a butyronitrile, benzonitrile, orany combination thereof; alternatively, acetonitrile; alternatively,propionitrile; alternatively, a butyronitrile; or alternatively,benzonitrile

Generally, each ether ligand independently can be a C₂ to C₄₀, C₂ toC₃₀, or C₂ to C₂₀ ether. In an aspect, each ether ligand independentlycan be a C₂ to C₄₀ aliphatic ether, a C₃ to C₄₀ aliphatic cyclic ether,a C₄ to C₄₀ aromatic cyclic ether; alternatively, a C₂ to C₄₀ aliphaticacyclic ether or a C₃ to C₄₀ aliphatic cyclic ether; alternatively, a C₂to C₄₀ aliphatic acyclic ether; alternatively, a C₃ to C₄₀ aliphaticcyclic ether; or alternatively, a C₄ to C₄₀ aromatic cyclic ether. Insome aspects, each ether ligand independently can be a C₂ to C₃₀aliphatic ether, a C₃ to C₃₀ aliphatic cyclic ether, a C₄ to C₃₀aromatic cyclic ether; alternatively, a C₂ to C₃₀ aliphatic acyclicether or a C₃ to C₃₀ aliphatic cyclic ether; alternatively, a C₂ to C₃₀aliphatic acyclic ether; alternatively, a C₃ to C₃₀ aliphatic cyclicether; or alternatively, a C₄ to C₃₀ aromatic cyclic ether. In otheraspects, each ether ligand independently can be a C₂ to C₂₀ aliphaticether, a C₃ to C₂₀ aliphatic cyclic ether, a C₄ to C₂₀ aromatic cyclicether; alternatively, a C₂ to C₂₀ aliphatic acyclic ether or a C₃ to C₂₀aliphatic cyclic ether; alternatively, a C₂ to C₂₀ aliphatic acyclicether; alternatively, a C₃ to C₂₀ aliphatic cyclic ether; oralternatively, a C₄ to C₂₀ aromatic cyclic ether. In some aspects, eachether ligand independently can be dimethyl ether, diethyl ether, adipropyl ether, a dibutyl ether, methyl ethyl ether, a methyl propylether, a methyl butyl ether, tetrahydrofuran, a dihydrofuran,1,3-dioxolane, tetrahydropyran, a dihydropyran, a pyran, a dioxane,furan, benzofuran, isobenzofuran, dibenzofuran, diphenyl ether, aditolyl ether, or any combination thereof, alternatively, dimethylether, diethyl ether, a dipropyl ether, a dibutyl ether, methyl ethylether, a methyl propyl ether, a methyl butyl ether, or any combinationthereof, tetrahydrofuran, a dihydrofuran, 1,3-dioxolane,tetrahydropyran, a dihydropyran, a pyran, a dioxane, or any combinationthereof, furan, benzofuran, isobenzofuran, dibenzofuran, or anycombination thereof, diphenyl ether, a ditolyl ether, or any combinationthereof, alternatively, dimethyl ether; alternatively, diethyl ether;alternatively, a dipropyl ether; alternatively, a dibutyl ether;alternatively, methyl ethyl ether; alternatively, a methyl propyl ether;alternatively, a methyl butyl ether; alternatively, tetrahydrofuran;alternatively, a dihydrofuran; alternatively, 1,3-dioxolane;alternatively, tetrahydropyran; alternatively, a dihydropyran;alternatively, a pyran; alternatively, a dioxane; alternatively, furan;alternatively, benzofuran; alternatively, isobenzofuran; alternatively,dibenzofuran; alternatively, diphenyl ether; or alternatively, a ditolylether.

Throughout this disclosure, the monomeric form of the N²-phosphinylbicyclic amidine chromium salt complex has been depicted. It should benoted that while not explicitly shown, the N²-phosphinyl bicyclicamidine chromium salt complex can exist as dimeric structures having twomonoanion ligands bridging two chromium atoms. Consequently, while themonomeric N²-phosphinyl bicyclic amidine chromium salt complex isdepicted herein, these structures do not necessarily imply that adimeric form of the N²-phosphinyl bicyclic amidine chromium salt complexhaving bridging monomeric ligands are not formed and/or utilized.

In an aspect, the organoaluminum compound which can be utilized in thecatalyst systems and processes described herein can comprise analuminoxane, an alkylaluminum compound, or any combination thereof;alternatively, an aluminoxane; or alternatively, an alkylaluminumcompound. In an aspect, the alkylaluminum compound can be atrialkylaluminum, an alkylaluminum halide, an alkylaluminum alkoxide, orany combination thereof. In some aspects, the alkylaluminum compound canbe a trialkylaluminum, an alkylaluminum halide, or any combinationthereof; alternatively, a trialkylaluminum, an alkylaluminum alkoxide,or any combination thereof; or alternatively, a trialkylaluminum. Inother aspects, the alkylaluminum compound can be a trialkylaluminum;alternatively, an alkylaluminum halide; or alternatively, analkylaluminum alkoxide. In a non-limiting aspect, the aluminoxane canhave a repeating unit characterized by Formula I:

wherein R′ is a linear or branched alkyl group. Alkyl groups fororganoaluminum compounds are independently described herein and can beutilized without limitation to further describe the aluminoxanes havingFormula I. Generally, n of Formula I can be greater than 1; oralternatively, greater than 2. In an aspect, n can range from 2 to 15;or alternatively, from 3 to 10.

In an aspect, each halide of any alkylaluminum halide disclosed hereincan independently be fluoride, chloride, bromide, or iodide; oralternatively, chloride, bromide, or iodide. In an aspect, each halideof any alkylaluminum halide disclosed herein can be fluoride;alternatively, chloride; alternatively, bromide; or alternatively,iodide.

In an aspect, each alkyl group of any organoaluminum compound disclosedherein (alkylaluminum trialkylaluminum, alkylaluminum halide,alkylaluminum alkoxide or aluminoxane, among others) independently canbe a C₁ to C₂₀, C₁ to C₁₀, or C₁ to C₆ alkyl group. In an aspect, eachalkyl group of any organoaluminum compound disclosed hereinindependently can be a methyl group, an ethyl group, a propyl group, abutyl group, a pentyl group, a hexyl group, a heptyl group, or an octylgroup; alternatively, a methyl group, an ethyl group, a butyl group, ahexyl group, or an octyl group. In some aspects, each alkyl group of anyorganoaluminum compound disclosed herein independently can be a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an iso-butylgroup, an n-hexyl group, or an n-octyl group; alternatively, a methylgroup, an ethyl group, an n-butyl group, or an iso-butyl group;alternatively, a methyl group; alternatively, an ethyl group;alternatively, an n-propyl group; alternatively, an n-butyl group;alternatively, an iso-butyl group; alternatively, an n-hexyl group; oralternatively, an n-octyl group.

In an aspect, each alkoxide group of any alkylaluminum alkoxidedisclosed herein independently can be a C₁ to C₂₀, C₁ to C₁₀, or C₁ toC₆ alkoxy group. In an aspect, each alkoxide group of any alkylaluminumalkoxide disclosed herein independently can be a methoxy group, anethoxy group, a propoxy group, a butoxy group, a pentoxy group, a hexoxygroup, a heptoxy group, or an octoxy group; alternatively, a methoxygroup, an ethoxy group, a butoxy group, a hexoxy group, or an octoxygroup. In some aspects, each alkoxide group of any alkylaluminumalkoxide disclosed herein independently can be a methoxy group, anethoxy group, an n-propoxy group, an n-butoxy group, an iso-butoxygroup, an n-hexoxy group, or an n-octoxy group; alternatively, a methoxygroup, an ethoxy group, an n-butoxy group, or an iso-butoxy group;alternatively, a methoxy group; alternatively, an ethoxy group;alternatively, an n-propoxy group; alternatively, an n-butoxy group;alternatively, an iso-butoxy group; alternatively, an n-hexoxy group; oralternatively, an n-octoxy group.

In a non-limiting aspect, useful trialkylaluminum compounds can includetrimethylaluminum, triethylaluminum, tripropylaluminum,tributylaluminum, trihexylaluminum, trioctylaluminum, or mixturesthereof. In some non-limiting aspects, useful trialkylaluminum compoundscan include trimethylaluminum, triethylaluminum, tripropylaluminum,tri-n-butylaluminum, tri-isobutylaluminum, trihexylaluminum,tri-n-octylaluminum, or mixtures thereof; alternatively,triethylaluminum, tri-n-butylaluminum, tri-isobutylaluminum,trihexylaluminum, tri-n-octylaluminum, or mixtures thereof;alternatively, triethylaluminum, tri-n-butylaluminum, trihexylaluminum,tri-n-octylaluminum, or mixtures thereof. In other non-limiting aspects,useful trialkylaluminum compounds can include trimethylaluminum;alternatively, triethylaluminum; alternatively, tripropylaluminum;alternatively, tri-n-butylaluminum; alternatively, tri-isobutylaluminum;alternatively, trihexylaluminum; or alternatively, tri-n-octylaluminum.

In a non-limiting aspect, useful alkylaluminum halides can includediethylaluminum chloride, diethylaluminum bromide, ethylaluminumdichloride, ethylaluminum sesquichloride, and mixtures thereof. In somenon-limiting aspects, useful alkylaluminum halides can includediethylaluminum chloride, ethylaluminum dichloride, ethylaluminumsesquichloride, and mixtures thereof. In other non-limiting aspects,useful alkylaluminum halides can include diethylaluminum chloride;alternatively, diethylaluminum bromide; alternatively, ethylaluminumdichloride; or alternatively, ethylaluminum sesquichloride.

In a non-limiting aspect, useful aluminoxanes can includemethylaluminoxane (MAO), ethylaluminoxane, a modified methylaluminoxane(e.g., a MMAO), n-propylaluminoxane, isopropyl-aluminoxane,n-butylaluminoxane, sec-butylaluminoxane, iso-butylaluminoxane,t-butylaluminoxane, 1-pentylaluminoxane, 2-pentylaluminoxane,3-pentylaluminoxane, isopentylaluminoxane, neopentylaluminoxane, ormixtures thereof; In some non-limiting aspects, useful aluminoxanes caninclude methylaluminoxane (MAO), a modified methylaluminoxane (e.g., aMMAO), isobutyl aluminoxane, t-butylaluminoxane, or mixtures thereof. Inother non-limiting aspects, useful aluminoxanes can includemethylaluminoxane (MAO); alternatively, ethylaluminoxane; alternatively,a modified methylaluminoxane (e.g., a MMAO); alternatively,n-propylaluminoxane; alternatively, isopropylaluminoxane; alternatively,n-butylaluminoxane; alternatively, sec-butylaluminoxane; alternatively,iso-butylaluminoxane; alternatively, t-butylaluminoxane; alternatively,1-pentylaluminoxane; alternatively, 2-pentylaluminoxane; alternatively,3-pentylaluminoxane; alternatively, isopentylaluminoxane; oralternatively, neopentylaluminoxane.

In an aspect, the catalyst system can have any organoaluminum compoundand the N²-phosphinyl bicyclic amidine chromium salt complex (oralternatively, the chromium salt of the N²-phosphinyl bicyclic amidineratio that can form an active catalyst system. In an aspect, thecatalyst system can have a minimum aluminum of the organoaluminumcompound to chromium of the N²-phosphinyl bicyclic amidine chromium saltcomplex (or alternatively, chromium of the chromium salt in conjunctionwith the N²-phosphinyl bicyclic amidine molar ratio (i.e., minimum Al toCr molar ratio) of 10:1, 50:1, 75:1, or 100:1; alternatively oradditionally, a maximum aluminum of the organoaluminum compound tochromium of the in conjunction with the N²-phosphinyl bicyclic amidinechromium salt complex (or alternatively, chromium of the chromium saltin conjunction with the N²-phosphinyl bicyclic amidine molar ratio(i.e., maximum Al to Cr molar ratio) of 5,000:1, 3,000:1, 2,000:1,1,500:1, or 1,000:1. In an aspect, the catalyst system can have an Al toCr molar ratio ranging from any minimum Al to Cr molar ratio disclosedherein to any maximum Al to Cr molar ratio disclosed herein. In anon-limiting aspect, the Al to Cr molar ratio can range from 10:1 to5,000:1, from 50:1 to 3,000:1, from 75:1 to 2,000:1, from 100:1 to2,000:1, or from 100:1 to 1,000:1. Other Al to Cr molar ratio rangesthat can be utilized are readily apparent to those skilled in the artwith the aid of this disclosure.

When the catalyst system utilizes an N²-phosphinyl bicyclic amidine, achromium salt, and an organoaluminum compound, the catalyst system canhave (or the catalyst system can be formed at), the oligomer product canbe formed at, the reaction zone can have, or the reaction zone canoperate at any N²-phosphinyl bicyclic amidine to chromium of thechromium salt equivalent ratio which can form an oligomer product. In anaspect, the minimum N²-phosphinyl bicyclic amidine to chromium of thechromium salt molar ratio can be 0.8:1, 0.9:1, or 0.95:1; alternativelyor additionally, the maximum N²-phosphinyl bicyclic amidine to chromiumof the chromium salt molar ratio can be 4:1, 2:1, 1.5:1, or 1.1:1. In anaspect, the catalyst system can have (or the catalyst system can beformed at), the oligomer product can be formed at, the reaction zone canhave, or the reaction zone can operate at an N²-phosphinyl bicyclicamidine to chromium of the chromium salt molar ratio in the range of anyminimum N²-phosphinyl bicyclic amidine to chromium of the chromium saltmolar ratio disclosed herein to any maximum N²-phosphinyl bicyclicamidine to chromium of the chromium salt molar ratio disclosed herein.In a non-limiting aspects, the N²-phosphinyl bicyclic amidine tochromium of the chromium salt molar ratio can be in the range of 0.8:1to 4:1, from 0.9:1 to 2:1, from 0.9:1 to 1.5:1, from 0.95:1 to 1.5:1, orfrom 0.95:1 to 1.1:1. Other N²-phosphinyl bicyclic amidine to chromiumof the chromium salt molar ratio ranges that can be utilized are readilyapparent to those skilled in the art with the aid of this disclosure.

In an aspect, the processes described herein can comprise: a) contactingethylene and a catalyst system; and b) forming an oligomer product. Insome aspects, the processes described herein can comprise: a) contactingethylene, hydrogen, and a catalyst system; and b) forming an oligomerproduct. In some aspects, the oligomer product can be formed underconditions capable of forming an oligomer product. In some aspects, theoligomer product can be formed in a reaction zone. In an aspect, theprocess can be an ethylene oligomerization process; alternatively, anethylene trimerization process; alternatively, an ethylenetetramerization process; or alternatively, an ethylene trimerization andtetramerization process. In an aspect, the catalyst system can be formedin an organic liquid medium. In an aspect, the oligomer product can beformed in (or the reaction zone can include) an organic reaction medium.Generally, the organic liquid medium in which the catalyst system can beformed and the organic reaction medium in which the olefin and thecatalyst system can be contacted (or alternatively, in which theoligomer product can be formed) can be the same; or alternatively, canbe different. The catalyst system, the conditions under which theoligomer product can be formed (or alternatively, the conditions underwhich the reaction zone can operate), the organic liquid medium, theorganic reaction medium, and features of the oligomer product areindependently described herein and can be utilized in any combination,and without limitation, to further describe the processes describedherein.

In an aspect, the processes described herein can comprise: a) forming acatalyst system mixture comprising an N²-phosphinyl bicyclic amidinechromium salt complex and an organoaluminum compound (or alternatively,forming a catalyst system mixture comprising a chromium salt andN²-phosphinyl bicyclic amidine, a chromium salt, and an organoaluminumcompound); b) contacting the catalyst system mixture with ethylene; andc) forming an oligomer product. In some aspects, the step of contactingthe catalyst system mixture with ethylene can be a step of contactingthe catalyst system mixture with ethylene and hydrogen. In some aspects,the catalyst system mixture can further comprise an organic liquidmedium. In some aspects, the catalyst system mixture and ethylene, andoptionally hydrogen, can be contacted in or with an organic reactionmedium. In an aspect, the process can comprise: a) forming a catalystsystem mixture comprising, or consisting essentially of, theN²-phosphinyl bicyclic amidine chromium salt complex, an organoaluminumcompound, and an organic liquid medium (or alternatively, comprising theN²-phosphinyl bicyclic amidine, a chromium salt, an organoaluminumcompound, and an organic liquid medium); b) contacting the catalystsystem mixture with ethylene and an organic reaction medium; and c)forming an oligomer product. In some aspects, the step of contacting thecatalyst system mixture with ethylene and the organic liquid medium canbe a step of contacting the catalyst system mixture with ethylene, anorganic reaction medium, and hydrogen. In some aspects, the organicliquid medium and the organic reaction medium can be the same; oralternatively, the organic liquid medium and the organic reaction mediumcan be different. In some aspects, the oligomer product can be formed ina reaction zone. In some aspects, the oligomer product can be formedunder conditions capable of forming an oligomer product. TheN²-phosphinyl bicyclic amidine, the chromium salt, the N²-phosphinylbicyclic amidine chromium salt complex, the organoaluminum compound, theorganic liquid medium, the organic reaction medium, the conditions underwhich the oligomer product can be formed (or alternatively, theconditions under which the reaction zone can operate), and features ofthe oligomer product (among other independently described catalystsystem and process features) are independently described herein and canbe utilized, without limitation, and in any combination, to furtherdescribe the processes disclosed herein.

In an aspect, the processes described herein can comprise: a) forming acomposition comprising an N²-phosphinyl bicyclic amidine chromium saltcomplex (or alternatively, comprising an N²-phosphinyl bicyclic amidineand a chromium salt); b) forming a mixture comprising ethylene and anorganoaluminum compound; c) contacting the composition of step a) andthe mixture of step b); and d) forming an oligomer product. In someaspects, the mixture comprising ethylene and the organoaluminum compoundcan further comprise hydrogen. In some aspects, the compositioncomprising the N²-phosphinyl bicyclic amidine chromium salt complex (oralternatively, comprising the N²-phosphinyl bicyclic amidine and thechromium salt) can further comprise an organic liquid medium. In someaspects, the mixture comprising ethylene, an organoaluminum compound,and optionally hydrogen, can further comprise an organic reactionmedium. In an aspect, the process can comprise: a) forming a compositioncomprising, or consisting essentially of, the N²-phosphinyl bicyclicamidine chromium salt complex and an organic liquid medium (oralternatively, comprising the N²-phosphinyl bicyclic amidine, a chromiumsalt, and an organic liquid medium); b) forming a mixture comprisingethylene, an organoaluminum compound, optionally hydrogen, and anorganic reaction medium; c) contacting the composition of step a) andthe mixture of step b); and d) forming an oligomer product. In someaspects, the organic liquid medium and the organic reaction medium canbe the same; or alternatively, the organic liquid medium and the organicreaction medium can be different. In some aspects, the oligomer productcan be formed in a reaction zone. In some aspects, the oligomer productcan be formed under conditions capable of forming an oligomer product.The N²-phosphinyl bicyclic amidine, the chromium salt, the N²-phosphinylbicyclic amidine chromium salt complex, the organoaluminum compound, theorganic liquid medium, the organic reaction medium, the conditions underwhich the oligomer product can formed (or alternatively, the conditionsunder which the reaction zone can operate), and features of the oligomerproduct (among other composition, mixture, oligomer product and processfeatures) are independently described herein and can be utilized,without limitation, and in any combination, to further describe theprocesses described herein.

In an aspect, the processes described herein can comprise: a) contactingethylene and a catalyst system comprising an N²-phosphinyl bicyclicamidine chromium salt complex (or alternatively, contacting anN²-phosphinyl bicyclic amidine and a chromium salt); and b) forming anoligomer product in a reaction zone. In some aspects, the processesdescribed herein can comprise, a) contacting ethylene, hydrogen, and acatalyst system comprising the N²-phosphinyl bicyclic amidine chromiumsalt complex (or alternatively, contacting the N²-phosphinyl bicyclicamidine and a chromium salt); and b) forming an oligomer product in areaction zone. In other aspects, the processes described herein cancomprise: a) contacting ethylene and a catalyst system comprising theN²-phosphinyl bicyclic amidine chromium salt complex and anorganoaluminum compound (or alternatively, the N²-phosphinyl bicyclicamidine and a chromium salt and an organoaluminum compound); and b)forming an oligomer product in a reaction zone. In yet other aspects,the processes described herein can comprise, a) contacting ethylene,hydrogen, and a catalyst system comprising the N²-phosphinyl bicyclicamidine chromium salt complex and an organoaluminum compound (oralternatively, contacting an N²-phosphinyl bicyclic amidine, a chromiumsalt, and an organoaluminum compound); and b) forming an oligomerproduct in a reaction zone. In an aspect, the respective processes canfurther comprise forming a catalyst system mixture comprising thecatalyst system components. In some aspects, the catalyst system mixturecan be (or can be formed in) an organic liquid medium. In other aspectsof the respective processes, the oligomer product can be formed in (orthe reaction zone can include) an organic reaction medium. In someaspects, the organic liquid medium and the organic reaction medium canbe the same; or alternatively, the organic liquid medium and the organicreaction medium can be different. The N²-phosphinyl bicyclic amidine,the chromium salt, the N²-phosphinyl bicyclic amidine chromium saltcomplex, the organoaluminum compound, the organic liquid medium, theorganic reaction medium, the conditions under which the oligomer productcan be formed (or alternatively, the conditions under which the reactionzone can operate), and features of the oligomer product (among othercomposition, mixture, oligomer product, and process features) areindependently described herein and can be utilized, without limitation,and in any combination, to further describe the processes describedherein.

In an aspect, the processes described herein can be a batch process or acontinuous process. In some aspects, the reaction zone of any processdescribed herein can comprise any reactor which can oligomerize,trimerize, tetramerize, or trimerize and tetramerize ethylene to anoligomer product. In some aspects, the reaction zone can comprise one ormore reactors. In some aspects, the reaction zone can comprise a stirredtank reactor, a plug flow reactor, or any combination thereof;alternatively, a stirred tank reactor; or alternatively, a plug flowreactor. In an aspect, the reaction zone of any process described hereincan comprise an autoclave reactor, a continuous stirred tank reactor, aloop reactor, a gas phase reactor, a solution reactor, a tubularreactor, a recycle reactor, a bubble reactor, or any combinationthereof; alternatively, an autoclave reactor; alternatively, a stirredtank reactor; alternatively, a loop reactor; alternatively, a gas phasereactor; alternatively, a solution reactor; alternatively, a tubularreactor; alternatively, a recycle reactor; or alternatively, a bubblereactor. In some aspects, the reaction zone can comprise multiplereactors; or alternatively, only one reactor. When multiple reactors arepresent, each of the reactors can be the same; or alternatively, two ormore of the reactors can be different. The reaction zone can comprisesingle or multiple reactors of any type disclosed herein operating inbatch or continuous mode and/or in series or parallel.

The processes described herein can use an organic liquid medium and/oran organic reaction medium. Generally, the organic liquid medium and/orthe organic reaction medium can act as a solvent and/or a diluent in theprocesses described herein. In an aspect, the organic liquid mediumand/or the organic reaction medium can be a hydrocarbon, a halogenatedhydrocarbon, or a combination thereof. Hydrocarbons and halogenatedhydrocarbons which can be used as the organic liquid medium and/or theorganic reaction medium can include, for example, aliphatichydrocarbons, aromatic hydrocarbons, petroleum distillates, halogenatedaliphatic hydrocarbons, halogenated aromatic hydrocarbons, orcombinations thereof. Aliphatic hydrocarbons which can be used as theorganic liquid medium and/or the organic reaction medium include C₃ toC₂₀, C₄ to C₁₅, or C₅ to C₁₀ aliphatic hydrocarbons. The aliphatichydrocarbons which can be used as the organic liquid medium and/or theorganic reaction medium can be cyclic or acyclic and/or can be linear orbranched, unless otherwise specified. Non-limiting examples of suitableacyclic aliphatic hydrocarbon organic liquid mediums and/or organicreaction mediums that can be utilized include propane, isobutane,n-butane, butane (n-butane or a mixture of linear and branched C₄acyclic aliphatic hydrocarbons), pentane (n-pentane or a mixture oflinear and branched C₅ acyclic aliphatic hydrocarbons), hexane (n-hexaneor a mixture of linear and branched C₆ acyclic aliphatic hydrocarbons),heptane (n-heptane or a mixture of linear and branched C₇ acyclicaliphatic hydrocarbons), octane (n-octane or a mixture of linear andbranched C₈ acyclic aliphatic hydrocarbons), or combinations thereof.Non-limiting examples of suitable cyclic aliphatic hydrocarbons whichcan be used as the organic liquid medium and/or the organic reactionmedium include cyclohexane, and methylcyclohexane. Aromatic hydrocarbonswhich can be used as the organic liquid medium and/or the organicreaction medium include C₆ to C₁₀ aromatic hydrocarbons. Non-limitingexamples of suitable aromatic hydrocarbons that can be utilized as theorganic liquid medium and/or the organic reaction medium includebenzene, toluene, xylene (including ortho-xylene, meta-xylene,para-xylene, or mixtures thereof), ethylbenzene, or combinationsthereof. Halogenated aliphatic hydrocarbons which can be used as theorganic liquid medium and/or the organic reaction medium include C₁ toC₁₅, C₁ to C₁₀, or C₁ to C₅ halogenated aliphatic hydrocarbons. Thehalogenated aliphatic hydrocarbons which can be used as the organicliquid medium and/or the organic reaction medium can be cyclic oracyclic and/or can be linear or branched, unless otherwise specified.Non-limiting examples of suitable halogenated aliphatic hydrocarbonswhich can be utilized as the organic liquid medium and/or the organicreaction medium include methylene chloride, chloroform, carbontetrachloride, dichloroethane, trichloroethane, and any combinationthereof. Halogenated aromatic hydrocarbons which can be used as theorganic liquid medium and/or the organic reaction medium include C₆ toC₂₀ or C₆ to C₁₀ halogenated aromatic hydrocarbons. Non-limitingexamples of suitable halogenated aromatic hydrocarbons which can be usedas the organic liquid medium and/or the organic reaction medium includechlorobenzene, dichlorobenzene, or combinations thereof.

The choice of organic liquid medium and/or organic reaction medium canbe made on the basis of convenience in processing. For example,isobutane can be chosen to be compatible with the organic liquid mediumand/or organic reaction medium used in processes using the product(s) ofthe process described herein (e.g., using the product for the formationof polymer in a subsequent processing step). In some aspects, theorganic liquid medium and/or the organic reaction medium can be chosento be easily separable from one or more of the oligomers in the oligomerproduct. In some aspects, an oligomer of the oligomer product can beutilized as the organic liquid medium and/or the organic reactionmedium. For example, when 1-hexene is an oligomer of an ethylenetrimerization process or an ethylene trimerization and tetramerizationprocess, 1-hexene can be chosen as the organic liquid medium and/or theorganic reaction medium to decrease the need for separation. When1-octene is an oligomer of an ethylene tetramerization process orethylene trimerization and tetramerization process, 1-octene can bechosen as the organic liquid medium and/or the organic reaction mediumto decrease the need for separation.

Generally, the oligomer product that can be produced using the processesdescribed herein can be formed at conditions (or alternatively, thereaction zone can have any conditions), which can 1) facilitate oligomerproduct formation, 2) provide a desired oligomer product formation rate,3) provide acceptable catalyst system productivity, 4) provideacceptable oligomer selectivity, and/or 5) provide acceptable polymerformation. In an aspect, conditions under which the oligomer product canbe formed (or alternatively, the reaction zone can have conditionsthat), can include one or more of catalyst system component ratios,chromium concentration, pressure, ethylene partial pressure, ethyleneconcentration, presence of hydrogen (and its partial pressure and/orhydrogen to ethylene mass ratio), temperature, reaction time, singlepass ethylene conversion, and/or catalyst system productivity. Catalystsystem component ratios, chromium concentration, pressure, ethylenepartial pressure, ethylene concentration, presence of hydrogen (and itspartial pressure and/or hydrogen to ethylene mass ratio), temperature,reaction time, single pass ethylene conversion, and catalyst systemproductivity are independently described herein and these independentdescriptions can be used without limitation, and in any combination, todescribe condition(s) at which the oligomer product can be formed and/orcondition(s) at which the reaction zone can operate for any of theprocesses described herein.

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum aluminum of the organoaluminum to chromium ofthe N²-phosphinyl bicyclic amidine chromium salt complex (oralternatively, the chromium salt) molar ratio (Al to Cr molar ratio) of10:1, 50:1, 75:1, or 100:1; alternatively or additionally, ata maximumAl to Cr molar ratio of 5,000:1, 3,000:1, 2,000:1, 1,500:1, or 1,000:1.In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at an Al to Cr molar ratio ranging from any minimum Al toCr molar ratio disclosed herein to any maximum Al to Cr molar ratiodisclosed herein. In a non-limiting aspect, the Al to Cr molar ratio canrange from 10:1 to 5,000:1, from 50:1 to 3,000:1, from 75:1 to 2,000:1,from 100:1 to 2,000:1, or from 100:1 to 1,000:1. Other Al to Cr molarratio ranges that can be utilized are readily apparent to those skilledin the art with the aid of this disclosure.

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum reaction zone chromium of the N²-phosphinylbicyclic amidine chromium salt complex (or alternatively, the chromiumof the chromium salt) concentration (i.e., minimum chromiumconcentration) of 1×10⁻⁶ Cr equivalents/liter, 1×10⁻⁵ Crequivalents/liter, or 5×10⁻⁴ Cr equivalents/liter; alternatively oradditionally, at a maximum reaction zone chromium of the N²-phosphinylbicyclic amidine chromium salt complex (or alternatively, chromium ofthe chromium salt) concentration (i.e., maximum chromium concentration)of 1 Cr equivalents/liter, 0.5 Cr equivalents/liter, or 0.1 Crequivalents/liter. In an aspect, the oligomer product can be formed (orthe reaction zone can operate) at a reaction zone chromium concentrationranging from any minimum chromium concentration disclosed herein to anymaximum chromium concentration disclosed herein. In a non-limitingaspect, the reaction zone chromium concentration can range from 1×10⁻⁶Cr equivalents/liter to 1 Cr equivalents/liter, from 1×10⁻⁵ Crequivalents/liter to 0.5 Cr equivalents/liter, or from 5×10⁻⁴ Crequivalents/liter to 0.1 Cr equivalents/liter. Other chromiumconcentration ranges that can be utilized are readily apparent to thoseskilled in the art with the aid of this disclosure.

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum pressure of 5 psi (34.5 kPa), 50 psi (345kPa), 100 psi (689 kPa), 150 psi (1.03 MPa), 250 psi (1.72 MPa), 500 psi(3.5 MPa), or 600 psi (4.1 MPa); alternatively or additionally, at amaximum pressure of 2,500 psi (17.2 MPa), 2,000 psi (13.8 MPa), 1,500psi (10.3 MPa), 1250 psi (8.62 MPa), or 1000 psi (6.89 MPa). In anaspect, the oligomer product can be formed (or the reaction zone canoperate) at a pressure ranging from any minimum pressure disclosedherein to any maximum pressure disclosed herein. In some non-limitingaspects, the oligomer product can be formed (or the reaction zone canoperate) at a pressure from 5 psi (34.5 kPa) to 2,500 psi (17.2 MPa),from 5 psi (34.5 kPa) to 2,000 psi (13.8 MPa), from 50 psi (345 kPa) to2,000 psi (13.8 MPa), from 100 psi (689 kPa) to 2,000 psi (13.8 MPa),from 100 psi (689 kPa) to 1,500 psi (10.3 MPa), from 150 psi (1.03 MPa)to 1500 psi (10.3 MPa), from 250 psi (1.72 MPa) to 1250 psi (8.62 MPa),from 500 psi (3.5 MPa) to 1250 psi (8.62 MPa), or from 600 psi (4.1 MPa)to 1000 psi (6.89 MPa). Other pressure ranges that can be utilized arereadily apparent to those skilled in the art with the aid of thisdisclosure.

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum ethylene partial pressure of 5 psi (34.5 kPa),50 psi (345 kPa), 100 psi (689 kPa), 150 psi (1.03 MPa), 250 psi (1.72MPa), or 500 psi (3.5 MPa); alternatively or additionally, at a maximumethylene partial pressure of 2,500 psi (17.2 MPa), 2,000 psi (13.8 MPa),1,500 psi (10.3 MPa), 1250 psi (8.62 MPa), or 1000 psi (6.89 MPa). In anaspect, the oligomer product can be formed (or the reaction zone canoperate) at an ethylene partial pressure ranging from any minimumethylene partial pressure disclosed herein to any maximum ethylenepartial pressure disclosed herein. In some non-limiting aspects, theoligomer product can be formed (or the reaction zone can operate) at anethylene partial pressure from 5 psi (34.5 kPa) to 2,500 psi (17.2 MPa),from 5 psi (34.5 kPa) to 2,000 psi (13.8 MPa), from 50 psi (345 kPa) to2,000 psi (13.8 MPa), from 100 psi (689 kPa) to 2,000 psi (13.8 MPa),from 100 psi (689 kPa) to 1,500 psi (10.3 MPa), from 150 psi (1.03 MPa)to 1250 psi (8.62 MPa), from 250 psi (1.72 MPa) to 1000 psi (6.89 MPa),or from 500 psi (3.5 MPa) to 1000 psi (6.89 MPa). Other ethylene partialpressure ranges are readily apparent to those skilled in the art withthe aid of this disclosure.

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum ethylene concentration of 4 mass %, 10 mass %,25 mass %, 35 mass %, or 40 mass % based upon the total mass in thereaction zone; alternatively or additionally, at a maximum ethyleneconcentration of 70 mass %, 65 mass %, 60 mass %, 55 mass %, 50 mass %,or 48 mass % based upon the total mass in the reaction zone. In anaspect, the oligomer product can be formed (or the reaction zone canoperate) at an ethylene concentration ranging from any minimum ethyleneconcentration disclosed herein to any maximum ethylene concentrationdisclosed herein. In some non-limiting aspects, the oligomer product canbe formed (or the reaction zone can operate) at an ethyleneconcentration in a range of from 4 mass % to 70 mass %, from 4 mass % to65 mass %, from 10 mass % to 60 mass %, from 25 mass % to 60 mass %,from 25 mass % to 55 mass %, from 35 mass % to 50 mass %, or from 40mass % to 48 mass % based upon the total mass in the reaction zone.Other ethylene concentration ranges that can be utilized are readilyapparent to those skilled in the art with the aid of this disclosure.

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum ethylene:chromium mass ratio of 50,000:1,150,000:1, 250,000:1, or 400,000:1; alternatively, or additionally, at amaximum ethylene:chromium mass ratio of 5,000,000:1, 2,500,000:1,1,500,000:1, or 1,000,000:1. In an aspect, the oligomer product can beformed (or the reaction zone can operate) at an ethylene:chromium massratio ranging from any minimum ethylene:chromium mass ratio disclosedherein to any maximum ethylene:chromium mass ratio disclosed herein. Insome non-limiting aspects, the oligomer product can be formed (or thereaction zone can operate) at an ethylene:chromium mass ratio in therange of 50,000:1 to 5,000,000:1, 150,000:1 to 2,500,000:1, 250,000:1 to1,500,000:1, or 400,000:1 to 1,000,000:1. Other ethylene:chromium massratio ranges that can be utilized are readily apparent to those skilledin the art with the aid of this disclosure. Generally, theethylene:chromium mass ratio is based upon the chromium in theN²-phosphinyl bicyclic amidine chromium salt complex (or alternatively,the chromium salt).

In an aspect wherein hydrogen is utilized, the oligomer product can beformed (or the reaction zone can operate) at a minimum hydrogen partialpressure of 1 psi (6.9 kPa), 2 psi (14 kPa), 5 psi (34 kPa), 10 psi (69kPa), or 15 psi (103 kPa); alternatively or additionally at a maximumhydrogen partial pressure of 200 psi (1.4 MPa), 150 psi (1.03 MPa), 100psi (689 kPa), 75 psi (517 kPa), or 50 psi (345 kPa). In an aspect, theoligomer product can be formed (or the reaction zone can operate) at ahydrogen partial pressure ranging from any minimum hydrogen partialpressure disclosed herein to any maximum hydrogen partial pressuredisclosed herein. In some non-limiting aspects, wherein hydrogen isutilized, the oligomer product can be formed (or the reaction zone canoperate) at a hydrogen partial pressure from 1 psi (6.9 kPa) to 200 psi(1.4 MPa), from 2 psi (14 kPa) to 150 psi (1.03 MPa), from 5 psi (34kPa) to 100 psi (689 kPa), from 10 psi (69 kPa) to 75 psi (517 kPa), orfrom 15 psi (103 kPa) to 50 psi (345 kPa). Other hydrogen partialpressure ranges that can be utilized are readily apparent to thoseskilled in the art with the aid of this disclosure.

In an aspect wherein hydrogen is utilized, the oligomer product can beformed (or the reaction zone can operate) at a minimum hydrogen toethylene mass ratio of (0.05 g hydrogen)/(kg ethylene), (0.1 ghydrogen)/(kg ethylene), (0.25 g hydrogen)/(kg ethylene), (0.4 ghydrogen)/(kg ethylene), or (0.5 g hydrogen)/(kg ethylene);alternatively or additionally, at a maximum hydrogen to ethylene massratio of (5 g hydrogen)/(kg ethylene), (3 g hydrogen)/(kg ethylene),(2.5 g hydrogen)/(kg ethylene), (2 g hydrogen)/(kg ethylene), or (1.5 ghydrogen)/(kg ethylene). In an aspect, the oligomer product can beformed (or the reaction zone can operate) at a hydrogen to ethylene massratio ranging from any minimum hydrogen to ethylene mass ratio disclosedherein to any maximum hydrogen to ethylene mass ratio disclosed herein.In some non-limiting aspects, the oligomer product can be formed (or thereaction zone can operate) at a hydrogen to ethylene mass ratio from(0.05 g hydrogen)/(kg ethylene) to (5 g hydrogen)/(kg ethylene), from(0.1 g hydrogen)/(kg ethylene) to (5 g hydrogen)/(kg ethylene), from(0.25 g hydrogen)/(kg ethylene) to (4 g hydrogen)/(kg ethylene), from(0.4 g hydrogen)/(kg ethylene) to (3 g hydrogen)/(kg ethylene), from(0.4 g hydrogen)/(kg ethylene) to (2.5 g hydrogen)/(kg ethylene), from(0.4 g hydrogen)/(kg ethylene) to (2 g hydrogen)/(kg ethylene), from(0.5 g hydrogen)/(kg ethylene) to (2 g hydrogen)/(kg ethylene), or from(0.5 g hydrogen)/(kg ethylene) to (1.5 g hydrogen)/(kg ethylene). Otherhydrogen to ethylene mass ratio ranges that can be utilized are readilyapparent to those skilled in the art with the aid of this disclosure.

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum hydrogen:chromium of the N²-phosphinylbicyclic amidine chromium salt complex (or alternatively, the chromiumsalt) mass ratio (minimum hydrogen:chromium mass ratio) of 1:1, 50:1,100:1, or 200:1; alternatively or additionally, at a maximumhydrogen:chromium of the N²-phosphinyl bicyclic amidine chromium saltcomplex (or alternatively, the chromium salt) mass ratio (maximumhydrogen:chromium mass ratio) of 100,000:1, 50,000:1, 10,000:1, or3,000:1. In an aspect, the oligomer product can be formed (or thereaction zone can operate) at a hydrogen:chromium of the N²-phosphinylbicyclic amidine chromium salt complex (or alternatively, the chromiumsalt) mass ratio (hydrogen:chromium mass ratio) ranging from any minimumhydrogen:chromium mass ratio disclosed herein to any maximumhydrogen:chromium mass ratio disclosed herein. In some non-limitingaspects, the oligomer product can be formed (or the reaction zone canoperate) at a hydrogen:chromium mass ratio in the range of 1:1 to100,000:1, 50:1 to 50,000:1, 100:1 to 10,000:1, or 200:1 to 3,000:1.Other hydrogen:chromium mass ratio ranges that can be utilized arereadily apparent to those skilled in the art with the aid of thisdisclosure. Generally, the hydrogen:chromium mass ratio is based uponthe chromium in the N²-phosphinyl bicyclic amidine chromium salt complex(or alternatively, the chromium salt).

In an aspect, the oligomer product can be formed (or the reaction zonecan operate) at a minimum temperature of 0° C., 25° C., 40° C., or 50°C.; alternatively, or additionally, at a maximum temperature of 200° C.,150° C., 100° C., or 90° C. In an aspect, the oligomer product can beformed (or the reaction zone can operate) at a temperature ranging fromany minimum temperature disclosed herein to any maximum temperaturedisclosed herein. In some non-limiting aspects, the oligomer product canbe formed (or the reaction zone can operate) at a temperature from 0° C.to 200° C., from 25° C. to 150° C., from 40° C. to 100° C., from 50° C.to 100° C., or from 50° C. to 90° C. Other temperature ranges that canbe utilized are readily apparent to those skilled in the art with theaid of this disclosure.

The reaction time (or residence time or average residence time) in thereaction zone can comprise any time that can produce the desiredquantity of oligomer product; alternatively, any reaction time (orresidence time) that can provide a desired catalyst system productivity;alternatively, any reaction time (or residence time or average residencetime) that can provide a desired ethylene conversion. Relating toforming the oligomer product, the oligomer product can be formed over aperiod of time (or an average residence time) that can produce thedesired quantity of olefin product or polymer product, provide thedesired catalyst system productivity, and/or provide the desiredconversion of monomer. In some aspects, the reaction time (or residencetime or average residence time) can range from 1 minute to 5 hours;alternatively, can range from 5 minutes to 2.5 hours; alternatively, canrange from 10 minutes to 2 hours; or alternatively, can range from 15minutes to 1.5 hours. In some aspects (in continuous process aspects),the reaction time (or residence time or average residence time) can bestated as an average reaction time (or average residence time) and canrange from 1 minute to 5 hours; alternatively, can range from 5 minutesto 2.5 hours; alternatively, can range from 10 minutes to 2 hours; oralternatively, can range from 15 minutes to 1.5 hours.

In an aspect, the processes described herein can have an ethyleneconversion of at least 30%, 35%, 40%, or 45%. In another aspect, theethylene conversion can be a single pass conversion of at least 30%,35%, 40%, or 45%.

In an aspect, the processes described herein can have a catalyst systemproductivity of greater than 10,000 grams, 50,000 grams, 100,000 grams,150,000 grams, 200,000 grams, 300,000 grams, or 400,000 grams (C₆+C₈)per gram of chromium (g (C₆+C₈)/g Cr).

Depending upon the catalyst system utilized, the processes describedherein can be an ethylene oligomerization process, an ethylenetrimerization process, an ethylene tetramerization process, or anethylene trimerization and tetramerization process; alternatively, anethylene oligomerization process; alternatively, an ethylenetrimerization process; alternatively, an ethylene tetramerizationprocess; or alternatively an ethylene trimerization and tetramerizationprocess. In ethylene trimerization aspects, the oligomer product cancomprise at least 70 wt. % hexenes, at least 75 wt. % hexenes, at least80 wt. % hexenes, at least 85 wt. % hexenes, or at least 90 wt. %hexenes based upon the weight of the oligomer product. In some ethylenetrimerization aspects, the oligomer product can comprise from 70 wt. %to 99.8 wt. % hexenes, from 75 wt. % to 99.7 wt. % hexenes, or from 80wt. % to 99.6 wt. % hexenes based upon the weight of the oligomerproduct. In ethylene tetramerization aspects, the oligomer product cancomprise at least 70 wt. % octenes, at least 75 wt. % octenes, at least80 wt. % octenes, at least 85 wt. % octenes, or at least 90 wt. %octenes based upon the weight of the oligomer product. In some ethylenetetramerization aspects, the oligomer product can comprise from 70 wt. %to 99.8 wt. % octenes, from 75 wt. % to 99.7 wt. % octenes, or from 80wt. % to 99.6 wt. % octenes based upon the weight of the oligomerproduct. In ethylene trimerization and tetramerization aspects, theoligomer product can comprise at least 70 wt. % hexenes and octenes, atleast 75 wt. % hexenes and octenes, at least 80 wt. % hexenes andoctenes, at least 85 wt. % hexenes and octenes, or at least 90 wt. %hexenes and octenes based upon the weight of the oligomer product. Insome ethylene trimerization and tetramerization aspects, the oligomerproduct can comprise from 70 wt. % to 99.8 wt. % hexenes and octenes,from 75 wt. % to 99.7 wt. % hexenes and octenes, or from 80 wt. % to99.6 wt. % hexenes and octenes based upon the weight of the oligomerproduct.

In ethylene oligomerization, ethylene trimerization, or ethylenetrimerization and tetramerization aspects, the ethylene trimer cancomprise at least 90 wt. % 1-hexene; alternatively, at least 92.5 wt. %1-hexene; alternatively, at least 95 wt. % 1-hexene; alternatively, atleast 97 wt. % 1-hexene; or alternatively, at least 98 wt. % 1-hexene byweight of the ethylene trimer. In other ethylene oligomerization,ethylene trimerization, or ethylene trimerization and tetramerizationaspects, the ethylene trimer can comprise from 85 wt. % to 99.9 wt. %1-hexene; alternatively, from 87.5 wt. % to 99.9 wt. % 1-hexene;alternatively, from 90 wt. % to 99.9 wt. % 1-hexene; alternatively, from92.5 wt. % to 99.9 wt. % 1-hexene; alternatively, from 95 wt. % to 99.9wt. % 1-hexene; alternatively, from 97 wt. % to 99.9 wt. % 1-hexene; oralternatively, from 98 wt. % to 99.9 wt. % 1-hexene by weight of theethylene trimer.

In ethylene oligomerization, ethylene tetramerization, or ethylenetrimerization and tetramerization aspects, the ethylene tetramer cancomprise at least 85 wt. % 1-octene; alternatively, at least 90 wt. %1-octene; alternatively, at least 92.5 wt. % 1-octene; alternatively, atleast 95 wt. % 1-octene; alternatively, at least 97 wt. % 1-octene; oralternatively, at least 98 wt. % 1-octene by weight of the ethylenetetramer. In other ethylene oligomerization, ethylene tetramerization,or ethylene trimerization and tetramerization aspects, the ethylenetetramer can comprise from 85 wt. % to 99.9 wt. % 1-octene;alternatively, from 90 wt. % to 99.9 wt. % 1-octene; alternatively, from92.5 wt. % to 99.9 wt. % 1-octene; alternatively, from 95 wt. % to 99.9wt. % 1-octene; alternatively, from 97 wt. % to 99.9 wt. % 1-octene; oralternatively, from 98 wt. % to 99.9 wt. % 1-octene by weight of theethylene tetramer.

In some aspects, the processes described herein utilizing theN²-phosphinyl bicyclic amidine chromium salt complex (or alternatively,the N²-phosphinyl bicyclic amidine and the chromium salt) can produce anoligomer product comprising a mixture of C₈ and C₆ olefin productswherein the mass ratio of C₈ olefin products to C₆ olefin products canbe at least 0.5:1, at least 1:1, at least 1.5:1, or at least 1.75:1.

EXAMPLES

Methodology

Development of accurate density-functional theory (DFT), solvationmethods, and quantum mechanical tools have emerged that can enableprediction of products from molecular catalysts. One area of interest isto be able to predict the relative amounts of hexenes and/or octenesproduced by an ethylene trimerization and/or tetramerization catalystsystem. To be able to use computational methods to predict the relativeamounts of hexenes and/or octenes produced by a particular ethylenetrimerization and/or tetramerization catalyst, a plausible mechanismcapable of demonstrating hexenes and/or octenes selectivity is needed.Using computational and experimental studies of i) Britovsek, G. J. P.and McGuinness, D. S. Chem. Eur. J. 2016, 22, 16891-16896, ii)Britovsek, G. J. P.; McGuinness, D. S.; Tomov, A. K. Catal. Sci.Technol. 2016, 6, 8234-8241, iii) Hossain, M. A.; Kim, H. S.; Houk, K.N. Cheong, M. Bull. Korean Chem. Soc. 2014, 35, 2835-2838, iv) Gong, M.;Liu, Z.; Li, Y.; Ma, Y.; Sun, Q.; Zhang, J.; Liu, B. Organometallics2016, 35, 972-981, v) Yang, Y.; Liu, Z.; Cheng, R.; He, X.; Liu, B.Organometallics 2014, 33, 2599-2607, vi) Qi, Y.; Zhong, L.; Liu, Z.;Qiu, P.; Cheng, R.; He, X.; Vanderbilt, J.; Liu, B. Organometallics2010, 29, 1588-1602, vii) Budzelaar, P. H. M. Can. J. Chem. 2009, 87,832-837, viii) Bhaduri, S.; Mukhopadhyay, S.; Kulkarni, S. A. J.Organomet. Chem. 2009, 694, 1297-1307, and ix) van Rensburg, W. J.;Grove, C.; Steynberg, J. P.; Stark, K. B.; Huyser, J. J.; Steynberg, P.J. Organometallics 2004, 23, 1207-1222, and experimental studies ofBartlett, S. A.; Moulin, J.; Tromp, M.; Reid, G.; Dent, A. J.; Cibin,G.; McGuinness, D. S.; Evans, J. ACS Catal. 2014, 4, 4201-4204, andwithout being limited by theory, Scheme 1 was developed as a plausiblecatalytic mechanism for ethylene trimerization and/or tetramerization.

In Scheme 1, precatalyst activation in the presence of ethylene cangenerate a low-valent Cr ethylene coordination species A. Oxidative C—Cbond coupling of the two ethylene units can form chromacyclopentane Bwhich can then coordinate with another ethylene to form thechromacyclopentane ethylene coordination species C followed by migratoryethylene insertion which can lead to the chromacycloheptane intermediateD. Intermediate D represents the common intermediate in the mechanisticpaths where the mechanisms for producing hexenes and octenes candiverge. Hexenes can be produced from the chromacycloheptaneintermediate D by β-hydrogen transfer via transition state TS1 to form1-hexene and a reduced Cr species which can then reform, in the presenceof ethylene, the low-valent Cr ethylene coordination species A. Octenescan be produced from the chromacycloheptane intermediate D by i)ethylene coordination to form the ethylene coordinated species E, ii)migratory insertion of ethylene through transition state TS2 to form thechromacyclononane species F, and iii) β-hydrogen transfer withinchromacyclononane species F to produce 1-octene and a reduced Cr specieswhich can then reform, in the presence of ethylene, the low-valent Crethylene coordination species A. This two-transition state model assumesdynamic equilibrium, often known as Curtin-Hammett conditions, where TS1and TS2 arise from the common chromacycloheptane intermediate D and afast equilibrium of possible intermediates leading up to TS1 and TS2.Via this mechanism selectivity can result from competitive β-hydrogentransfer of transition state TS1 and the migratory ethylene insertionfrom intermediate D through transition state TS2.

Without being limited by theory, the mechanism in Scheme 1 was thenapplied in a predictive method to allow for prediction of the relativeamounts of hexenes and/or octenes for previously unknown heteroatomicligand chromium salt complexes; for example, the herein disclosedN²-phosphinyl bicyclic amidine chromium salt complexes. In thispredictive method, Density Functional Theory calculations were appliedto experimentally evaluated N²-phosphinyl amidine chromium saltcomplexes to provide a correlation between the Density Functional Theorycalculations and the experimentally observed amounts of hexenes and/oroctenes. The correlation was then used to predict the amounts of hexenesand/or octenes produced by the herein disclosed N²-phosphinyl bicyclicamidine chromium salt complexes.

Without wishing to be limited by theory, Scheme 2 and Scheme 3illustrates the critical competing and selectivity determining reactioncoordinate pathways for producing hexenes and octenes usingN²-phosphinyl bicyclic amidine chromium salt complexes having StructureNPBACr I or Structure NPBACr II, respectively. These schemes include therespective general N²-phosphinyl bicyclic amidine chromium salt complexCrCH 1, the respective general N²-phosphinyl bicyclic amidine chromiumsalt complex CrCH 2, the respective general N²-phosphinyl bicyclicamidine chromium salt complex hexene transition state TS C6, and therespective general N²-phosphinyl bicyclic amidine chromium salt complexoctene transition state TS C8. Thus, for catalyst systems based upongeneral N²-phosphinyl bicyclic amidine chromium salt complexes havingStructure NPBACr I or Structure NPBACr II, the Gibbs free energydifference, ΔΔG^(‡), between: 1) the difference in the Gibbs free energyof the respective general N²-phosphinyl bicyclic amidine chromiumchromacycloheptane complex CrCH 1 and the respective generalN²-phosphinyl bicyclic amidine chromium salt complex hexene transitionstate TS C6; and 2) the difference in the Gibbs free energy of therespective general N²-phosphinyl bicyclic amidine chromiumchromacycloheptane complex CrCH 2 and the respective generalN²-phosphinyl bicyclic amidine chromium salt complex octene transitionstate TS C8 can be utilized in a predictive correlative method topredict the relative amounts of hexenes and/or octenes produced by anN²-phosphinyl bicyclic amidine chromium salt complex NPBACr I orStructure NPBACr II. Further, and without being limited by theory, sincethe respective general N²-phosphinyl bicyclic amidine chromiumchromacycloheptane complex CrCH 1 and the general N²-phosphinyl amidinechromium chromacycloheptane complex CrCH 2 are carbon-carbonchromacycloheptane rotational isomers of each other and it is expectedthat there is a low energy barrier for their interconversion, thecalculation of the Gibbs free energy difference, ΔΔG^(‡), can besimplified to the calculation of the Gibbs free energy differencebetween the respective general N²-phosphinyl bicyclic amidine chromiumsalt complex hexene transition state TS C6 and the respective generalN²-phosphinyl bicyclic amidine chromium salt complex octene transitionstate TS C8 (ΔΔG^(‡), in Scheme 2). Thus, the Gibbs free energydifference ΔΔG^(‡) was correlated with the experimentally observedamounts of hexenes and/or octenes produced by the experimentally testedN²-phosphinyl bicyclic amidine chromium salt complexes.

Density Functional Theory Calculations

Density Functional Theory calculations (specifically, unrestrictedUMO6L/Def2-TZVP//UM06/6-31G(d,p)(LANL2DZ) theory) combined with the SMDimplicit solvent model for cyclohexane (as implemented in Marenich, A.V.; Cramer, C. J.; Truhlar, D. G., J. Phys. Chem. B. 2009, 113,6378-6396) was used to calculate the Gibbs free energy of the cationicN²-phosphinyl bicyclic amidine chromium salt complex hexene transitionstate TS C6 (hereafter N²-phosphinyl bicyclic amidine chromium saltcomplex hexene transition state TS C6) and the cationic N²-phosphinylbicyclic amidine chromium salt complex octene transition state TS C8(hereafter N²-phosphinyl bicyclic amidine chromium salt complex hexenetransition state TS C8) and, for each N²-phosphinyl bicyclic amidinechromium salt complex. The Gibbs free energy difference between theN²-phosphinyl bicyclic amidine chromium salt complex hexene transitionstate TS C6 and the N²-phosphinyl bicyclic amidine chromium salt complexoctene transition state TS C8, ΔΔG^(‡), for each N²-phosphinyl bicyclicamidine chromium salt complex was then calculated. The calculations ofthe Gibbs free energy of the cationic N²-phosphinyl bicyclic amidinechromium salt complex transition state TS C6 (and other transition stateenergies used herein) and the cationic N²-phosphinyl bicyclic amidinechromium salt complex octene transition state TS C8 (and othertransition state energies used herein) were performed withoutconsidering the impact of the balancing anion.

The density functional theory calculations were carried out usingGaussian 09 (Frisch, M. J. et al. Gaussian 09™, Revision B.01, Gaussian,Inc.: Wallingford, Conn., USA, 2009).

Geometries to account for each degree of freedom and each spin state forthe N²-phosphinyl bicyclic amidine chromium salt complex hexenetransition state TS C6 (3 to 40 conformations depending on the exactligand) and the N²-phosphinyl bicyclic amidine chromium salt complexoctene transition state TS C8 (3 to 40 conformation depending on theexact ligand) for each N²-phosphinyl bicyclic amidine chromium saltcomplex were calculated using the pseudopotential LANL2DZ basis set forchromium (integrated into the Gaussian 09™, Revision B.01) and theunrestricted approximation of local Minnesota 06 density functionaltheory 6-31G(d,p) basis set (i.e., UM06/6-31G(d,p) basis set) for allother atoms in the N²-phosphinyl bicyclic amidine chromium salttransition states. The transition-state structures with a complete setof force constants were calculated to ensure a single negativevibrational frequency that corresponded to the reaction coordinate.Additionally, the ground-state structure vibrational frequencies werecalculated to correspond to the second-order energy derivatives (i.e.,force constants) and were analyzed to confirm a local minimum energystructure. Additionally, zero point energies (ΔE_(ZPE(small))),vibrational, rotational, and translational energies (ΔU_(vib(small)),ΔU_(rot(small)), ΔU_(trans(small)), respectively), and vibrational,rotational, and translational entropies (ΔS_(vib(small)),ΔS_(rot(small)), ΔS_(trans(small)), respectively) were obtained to usein the calculation of the Gibbs free energy for the N²-phosphinylbicyclic amidine chromium salt complex hexene transition state TS C6 andthe N²-phosphinyl bicyclic amidine chromium salt complex octenetransition state TS C8.

The solvated geometries for the N²-phosphinyl bicyclic amidine chromiumsalt complex hexene transition state TS C6 conformation having thelowest energy and the N²-phosphinyl bicyclic amidine chromium saltcomplex octene transition state TS C8 conformation having the lowestenergy, along with any conformations having an energy relatively closeto the N²-phosphinyl bicyclic amidine chromium salt complex hexenetransition state TS C6 conformation having the lowest energy and theN²-phosphinyl bicyclic amidine chromium salt complex octene transitionstate TS C8 conformation having the lowest energy, were calculated usinga continuum model (SMD) that was parametrized and implemented inGaussian 09 for cyclohexane. The transition-state structures with acomplete set of force constants were calculated to ensure a singlenegative vibrational frequency that corresponded to the reactioncoordinate. Additionally, the ground-state structure vibrationalfrequencies were calculated to correspond to the second-order energyderivatives (i.e., force constants) and were analyzed to confirm a localminimum energy structure.

The total self-consistent field electronic energy containing theelectron kinetic and potential energies, and nuclear repulsion energy(E_((large))) and the standard state solvation free energy change(ΔG_(solv(large))) for the N²-phosphinyl bicyclic amidine chromium saltcomplex hexene transition state TS C6 and the N²-phosphinyl bicyclicamidine chromium salt complex octene transition state TS C8 were thencalculated using the unrestricted approximation of local Minnesota 06density functional theory Def2-TZVP basis set UMO6L/Def2-TZVP(downloaded from https://bse.pnl.gov/bse/portal on Jan. 1, 2016) toprovide accurate spin state energies and accurate calculations for weakdispersion forces.

The Gibbs free energy of the N²-phosphinyl bicyclic amidine chromiumsalt complex hexene transition state TS C6 and the N²-phosphinylbicyclic amidine chromium salt complex octene transition state TS C8were then calculated using the equationE_((large))+ΔE_(ZPE(small))+ΔU_(vib(small))+ΔU_(rot(small))+ΔU_(trans(small))+nRT−TΔS_(vib(small))−TΔS_(rot(small))−TΔS_(trans(small))+ΔG_(solv(large))where R is the ideal gas constant and T is the temperature (298 K wasused for these calculations). The Gibbs free energy difference, ΔΔG^(‡),between the N²-phosphinyl bicyclic amidine chromium salt complex hexenetransition state TS C6 and the N²-phosphinyl bicyclic amidine chromiumsalt complex octene transition state TS C8 for each N²-phosphinylbicyclic amidine chromium salt complex was then calculated as the Gibbsfree energy of N²-phosphinyl bicyclic amidine chromium salt complexhexene transition state TS C6 minus the Gibbs free energy of theN²-phosphinyl bicyclic amidine chromium salt complex octene transitionstate TS C8.

Table 1 provides the calculated ΔΔG^(‡) values between N²-phosphinylamidine chromium salt complex hexene transition state TS C6 andN²-phosphinyl amidine chromium salt complex octene transition state TSC8 for five N²-phosphinyl amidine chromium salt complexes (NPA 1-NPA 5)for which experimental data using a chromium complex having theindicated N²-phosphinyl amidine ligand had been determined (see EthyleneOligomerization Examples). Table 1 further provides predictive values ofΔΔG^(‡) and product distribution for N²-phosphinyl bicyclic amidinechromium salt complexes using the ligand having Structure NPBA 1, NPBA2, and NPBA3.

Ethylene Oligomerizations Examples

A 1L stainless steel autoclave reactor was dried under vacuum at 110° C.for at least 8 hours prior to use. The reactor was then cooled to 50° C.In a drybox, a 20 mL glass vial was charged with an N²-phosphinylamidine chromium complex (0.009-0.010 mmol), ethylbenzene (2.00 g),MMAO-3A (400-800 equivalents), Al (7 wt. % Al solution in heptanes), andan internal standard (n-nonane, 1.00 g). This solution was then added toa 0.5 L glass charger containing cyclohexane (400 mL). The combinedsolution was removed from the drybox and charged into the 1 L stainlesssteel autoclave reactor under static vacuum. The reactor was then heatedto 5° C. below the reaction temperature and charged with hydrogen.Ethylene was then charged to the reactor on-demand to maintain thedesired operating pressure. After 30 minutes, water cooling was appliedto the 1L stainless steel autoclave reactor to terminate the ethyleneoligomerization reaction. When the reactor temperature reached 35° C.,the unreacted ethylene and hydrogen gas was vented to the atmosphere. Aliquid sample of the 1L stainless steel autoclave reactor contents wasthen collected at room temperature and analyzed by gas chromatography.The reactor solids were collected by filtering the reaction and cleaningthe reactor walls and cooling coil. The mass % of the trimer (1-hexene)and tetramer (1-octene) observed in the oligomer product (as apercentage of the total trimer and tetramer produced) for each ofchromium salt complexes of N²-phosphinyl amidine ligands 1-5 arereported in Table 1.

TABLE 1 Experimentally Calculated Values Observed Values ΔΔG‡, Trimer,Tetramer, P—Cr—N Trimer, Tetramer, Ligand† kcal mass % mass % BondAngle, ° mass % mass %

2.4 99.1 0.9 77 93.6 0.9

−0.5 82.6 17.4 76 85.4 12

−0.2 86.9 13.1 75 79.3 15

−1.3 65.9 34.1 76 65.2 30.5

−1.3 66.9 33.1 77 52.2 33.7

−3.23 20.3 79.7 78.7/78.5 ND ND

−1.46 63.4 36.6 77.2/76.8 ND ND

3.61 99.8 0.02 77.2/75.2 ND ND †^(t)Bu = tert-butyl, ^(i)Pr = isopropyl,Ph = phenyl, Et = ethylCorrelation of ΔΔG^(‡) and C₆/C₈ Mass Ratio

The calculated ΔΔG^(‡) for the experimentally evaluated chromium saltcomplexes of the N²-phosphinyl amidine ligands NPA 1-NPA 5 were found toprovide a good linear correlation with the natural logarithm of the C₆to C₈ mass ratio, ln(mass C₆/mass C₈) (or alternatively ln(C₆/C₈),observed when the chromium salt complexes of the five N²-phosphinylamidine ligands were utilized in a catalyst system for oligomerizingethylene (see Ethylene Oligomerization Examples provided herein). FIG. 1provides a graph of the calculated ΔΔG^(‡) versus ln(C₆/C₈) for thechromium salt complexes of the five N²-phosphinyl amidine ligands inTable 1. The least squares fitted line of this data had a correlationcoefficient, R², of 0.9744 indicating a good correlation between ΔΔG^(‡)and the experimentally observed mass of hexenes and octenes. Use of theΔΔG^(‡) versus ln(C₆/C₅) trend line to calculate the ln(C₆/C₅) for thechromium salt complex of the N²-phosphinyl bicyclic amidine ligandshaving structures NPBA 1-NPBA 3. The linear correlation provide in FIG.1 was then utilized to determine the ln(C₆/C₈) and the correspondingmass % C₆ and mass % of C₈ provided in Table 1.

Synthesis of N²-phosphinyl Amidine Ligands

The synthesis of the N²-phosphinyl amidine ligands (NPA 1-NPA 5) was,and the potential synthesis of the N²-phosphinyl bicyclic amidineligands of the present disclosure (e.g., NPBA 1, NPBA 2, and NPBA 3) canbe performed using the general synthetic procedures as provided in U.S.patent application Ser. No. 15/166,991 and U.S. patent application Ser.No. 15/171,170 which are incorporated herein by reference in theirentirety.

ADDITIONAL DISCLOSURE

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an aspect of thepresent disclosure. Thus, the claims are a further description and arean addition to the detailed description of the present disclosure. Thedisclosures of all patents, patent applications, and publications citedherein are hereby incorporated by reference.

Statement 1. A catalyst system comprising i) (a) an N²-phosphinylbicyclic amidine chromium salt complex having Structure NPBACr I orStructure NPBACr II

or (b) a chromium salt and an N²-phosphinyl bicyclic amidine havingStructure NPBA I or Structure NPBA II

wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently are ahydrogen or a C₁ to C₃₀ organyl group, L¹ and L² independently are a C₁to C₃₀ a hydrocarbylene group, R⁴ and R⁵ independently are a C₁ to C₃₀organyl group and R⁴ and R⁵ optionally are combined to form L⁴⁵ forminga ring or ring system including the phosphorus atom where L⁴⁵ is a C₁ toC₃₀ organylene group, CrX_(p) is a chromium salt where X is a monoanionand p is an integer from 2 to 6; and ii) an organoaluminum compound.

Statement 2. The catalyst system of statement 1, wherein theorganoaluminum compound comprises an aluminoxane.

Statement 3. The catalyst system of statement 2, wherein the aluminoxanecomprises methylaluminoxane (MAO), a modified methylaluminoxane,ethylaluminoxane, n-propylaluminoxane, iso-propylaluminoxane,n-butylaluminoxane, sec-butylaluminoxane, iso-butylaluminoxane, t-butylaluminoxane, 1-pentylaluminoxane, 2-pentylaluminoxane,3-pentylaluminoxane, iso-pentylaluminoxane, neopentylaluminoxane, ormixtures thereof.

Statement 4. The catalyst system of any one of statements 1 to 3, wherethe catalyst system has an aluminum of the organoaluminum compound tochromium of the chromium salt or chromium of the N²-phosphinyl bicyclicamidine chromium salt complex molar ratio in the range of 10:1 to5,000:1.

Statement 5. A process comprising: a) contacting i) ethylene, ii) acatalyst system comprising (a) (i) an N²-phosphinyl bicyclic amidinechromium salt complex having Structure NPBACr I or Structure NPBACr II

or (ii) an N²-phosphinyl bicyclic amidine having Structure NPBA I orStructure NPBA II

wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently are ahydrogen or a C₁ to C₃₀ organyl group, L¹ and L² independently are a C₁to C₃₀ a hydrocarbylene group, R⁴ and R⁵ independently are a C₁ to C₃₀organyl group and R⁴ and R⁵ optionally are combined to form L⁴⁵ forminga ring or ring system including the phosphorus atom where L⁴⁵ is a C₁ toC₃₀ organylene group, CrX_(p) is a chromium salt where X is a monoanionand p is an integer from 2 to 6, and (b) an organoaluminum compound, andiii) optionally an organic reaction medium; and b) forming an oligomerproduct in a reaction zone.

Statement 6. The process of statement 5, wherein the reaction zone hasany temperature disclosed herein (e.g., at least 0° C., 25° C., 40° C.,or 50° C., in a range of 0° C. to 200° C., 25° C. to 150° C., 40° C. to100° C., 50° C. to 100° C., or 50° C. to 90° C., among others).

Statement 7. The process of any one of statements 5 or 6, wherein thereaction zone has any ethylene partial pressure disclosed herein (e.g.,at least 5 psi (34.5 kPa), 50 psi (345 kPa), 250 psi (1.72 MPa), or 500psi (3.5 MPa), in the range of 5 psi (34.5 kPa) to 2,500 psi (17.2 MPa),from 5 psi (34.5 kPa) to 2,000 psi (13.8 MPa), from 100 psi (689 kPa) to2,000 psi (13.8 MPa), from 500 psi (3.5 MPa) to 1500 psi (10.3 MPa),from 150 psi (1.03 MPa) to 1250 psi (8.62 MPa), or from 250 psi (1.72MPa) to 1000 psi (6.89 MPa), among others).

Statement 8. The process of any one of statements 5 to 7, wherein thereaction zone has any ethylene:chromium mass ratio disclosed herein(e.g., 50,000:1, 150,000:1, 250,000:1, or 400,000:1, in the range of50,000:1 to 5,000,000:1, 150,000:1 to 2,500,000:1, 250,000:1 to1,500,000:1, or 400,000:1 to 1,000,000:1, among others).

Statement 9. The process of Statement 8, wherein the organoaluminumcompound comprises, or consists essentially of, an aluminoxane.

Statement 10. The process of Statement 9, wherein the aluminoxanecomprises, or consists essentially of, methylaluminoxane (MAO), amodified methylaluminoxane, ethylaluminoxane, n-propylaluminoxane,iso-propylaluminoxane, n-butylaluminoxane, sec-butylaluminoxane,iso-butylaluminoxane, t-butyl aluminoxane, 1-pentylaluminoxane,2-pentylaluminoxane, 3-pentyl-aluminoxane, iso-pentylaluminoxane,neopentylaluminoxane, or mixtures thereof.

Statement 11. The process of any one of statements 5 to 10, wherein thereaction zone has any aluminum of the organoaluminum compound tochromium of the N²-phosphinyl bicyclic amidine chromium salt complexmolar ratio disclosed herein (e.g., at least 10:1, 50:1, 75:1, or 100:1,in the range of 10:1 to 5,000:1, from 50:1 to 3,000:1, from 50:1 to3,000:1, from 75:1 to 2,000:1, from 100:1 to 2,000:1, of from 100:1 to1,000:1, among others).

Statement 12. The process of any one of statements 5 to 11, wherein thereaction zone has any chromium of the N²-phosphinyl bicyclic amidinechromium salt complex concentration disclosed herein (e.g., at least1×10⁻⁶ Cr equivalents/liter, 1×10⁻⁵ Cr equivalents/liter, or 5×10⁻⁴ Crequivalents/liter, in the range of 1×10⁻⁶ Cr equivalents/liter to 1 Crequivalents/liter, 1×10⁻⁵ Cr equivalents/liter to 5×10⁻¹ Crequivalents/liter, 5×10⁻⁴ Cr equivalents/liter to 1×10⁻¹ Crequivalents/liter, among others).

Statement 13. The process of any one of statements 5 to 12, wherein thereaction zone has any ethylene concentration disclosed herein (e.g., atleast 4 mass %, 10 mass %, 25 mass %, 35 mass %, or 40 mass %, in therange of 4 mass % to 70 mass %, from 4 mass % to 60 mass %, from 10 mass% to 60 mass %, from 25 mass % to 55 mass %, 35 mass % to 50 mass %, or40 mass % to 48 mass %, among others) based upon the total mass in thereaction zone.

Statement 14. The process of any one of statements 5 to 13, wherein theprocess further comprises contacting hydrogen with the ethylene, thecatalyst system, and the optional organic reaction medium and thereaction zone has any hydrogen partial pressure disclosed herein (e.g.,at least 1 psi (6.9 kPa), 2 psi (14 kPa), 5 psi (34 kPa), 10 psi (69kPa), or 15 psi (103 kPa), in the range of 1 psi (6.9 kPa) to 200 psi(1.4 MPa), from 5 psi (34 kPa) to 150 psi (1.03 MPa), from 10 psi (69kPa) to 100 psi (689 kPa), or from 15 psi (100 kPa) to 75 psig (517kPa), among others).

Statement 15. The process of any one of statements 5 to 13, wherein theprocess further comprises contacting hydrogen with the ethylene, thecatalyst system, and the optional organic reaction medium and thereaction zone has any hydrogen to ethylene mass ratio disclosed herein(e.g., at least (0.05 g hydrogen)/(kg ethylene), (0.1 g hydrogen)/(kgethylene), (0.25 g hydrogen)/(kg ethylene), (0.4 g hydrogen)/(kgethylene), or (0.5 g hydrogen)/(kg ethylene), in the range of (0.05 ghydrogen)/(kg ethylene) to (5 g hydrogen)/(kg ethylene), from (0.25 ghydrogen)/(kg ethylene) to (5 g hydrogen)/(kg ethylene), (0.25 ghydrogen)/(kg ethylene) to (4 g hydrogen)/(kg ethylene), (0.4 ghydrogen)/(kg ethylene) to (3 g hydrogen)/(kg ethylene), (0.4 ghydrogen)/(kg ethylene) to (2.5 g hydrogen)/(kg ethylene), (0.4 ghydrogen)/(kg ethylene) to (2 g hydrogen)/(kg ethylene), or (0.5 ghydrogen)/(kg ethylene) to (2 g hydrogen)/(kg ethylene), among others).

Statement 16. The process of statement 14 or 15, wherein the processfurther comprises contacting hydrogen with the ethylene, the catalystsystem, and the optional organic reaction medium and the reaction zonehas any hydrogen:chromium mass ratio disclosed herein (e.g., at least1:1, 50:1, 100:1, or 200:1, in the range of 1:1 to 100,000:1, 50:1 to50,000:1, 100:1 to 10,000:1, or 200:1 to 3,000:1, among others).

Statement 17. The process of any one of statements 5 to 16, wherein theliquid oligomer product comprises any amount of hexenes, octenes, or anycombination thereof disclosed herein.

Statement 18. The process of any one of statements 5 to 17, wherein anethylene trimer has any 1-hexene content disclosed herein (e.g., atleast 90 wt. %, 92.5 wt. %, 95 wt. %, 97 wt. %, or 98 wt. % 1-hexene,from 85 wt. % to 99.9 wt. %, from 87.5 wt. % to 99.9 wt. %, from 90 wt.% to 99.9 wt. %, from 92.5 wt. % to 99.9 wt. %, from 95 wt. % to 99.9wt. %, from 97 wt. % to 99.9 wt. %; or from 98 wt. % to 99.9 wt. %1-hexene, among others).

Statement 19. The process of any one of statements 5 to 18, wherein anethylene tetramer has any 1-octene content disclosed herein (e.g., 90wt. %, 92.5 wt. %, at least 95 wt. %, at least 97 wt. % 1-octene, or 98wt. % 1-octene, from 90 wt. % to 99.9 wt. %, from 92.5 wt. % to 99.9 wt.%, from 95 wt. % to 99.9 wt. %, from 97 wt. % to 99.9 wt. %, or from 98wt. % to 99.9 wt. % 1-octene, among others).

Statement 20. The process of any one of statements 5 to 20, wherein theoligomer product has any C₈/C₆ ratio disclosed herein (e.g., at least0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.7:1 or 1:1 or alternatively, from0.1:1 to 10:1, from 0.2:1 to 7.5:1, from 0.3:1 to 5:1, 0.3:1 to 4:1,from 0.4:1 to 3:1, from 0.5:1 to 3:1, from 0.7:1 to 3:1, or from 1:1 to3:1, among others).

Statement 21. The catalyst system of any one of statements 1 to 4, orthe process of any one of statements 5 to 20, wherein L¹ is a methylenegroup, an eth-1,2-ylene group, or a prop-1,3-ylene group.

Statement 22. The catalyst system of any one of statements 1 to 4 or 21,or the process of any one of statements 5 to 21, wherein L² is amethylene group or an eth-1,2-ylene group.

Statement 23. The catalyst system of any one of statements 1 to 4 or 21to 22, or the process of any one of statements 5 to 22, wherein R¹¹,R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently is a hydrogen or anyC₁ to C₃₀ organyl group consisting of inert functional groups describedherein.

Statement 24. The catalyst system of any one of statements 1 to 4 or 21to 22, or the process of any one of statements 5 to 22, wherein R¹¹,R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently are a hydrogen orany C₁ to Cao hydrocarbyl group described herein.

Statement 25. The catalyst system of any one of statements 1-4 or 21 to24, or the process of any one of statements 5 to 24, wherein R⁴ and R⁵independently are a C₁ to C₁₅ alkyl group, a C₄ to C₂₀ cycloalkyl group,a C₄ to C₂₀ substituted cycloalkyl group, a C₆ to C₂₀ aryl group, or aC₆ to C₂₀ substituted aryl group.

Statement 26. The catalyst system of any one of statements 1 to 4 or 21to 24, or the process of any one of statements 5 to 24, wherein R⁴ andR⁵ independently are a C₁ to C₅ alkyl group, a C₄ to C₁₀ cycloalkylgroup, a phenyl group, or a C₆ to C₁₀ aryl group.

Statement 27. The catalyst system of any one of statements 1 to 4 or 21to 24, or the process of any one of statements 5 to 24, where R⁴ and R⁵are combined to form L⁴⁵ forming a ring or ring system including thephosphorus atom where L⁴⁵ is a C₁ to C₂₀ hydrocarbylene group.

Statement 28. The catalyst system of any one of statements 1 to 4 or 21to 27, or the process of any one of statements 5 to 27, wherein each Xindependently is a halide, a carboxylate, or a β-diketonate.

Statement 29. The catalyst system of any one of statements 1 to 4 or 21to 27, or the process of any one of statements 5 to 27, wherein thechromium salt is a chromium(III) carboxylate, a chromium(III)β-diketonate, or a chromium(III) halide.

Statement 30. The catalyst system of any one of statements 1 to 4 or 21to 27, or the process of any one of statements 5 to 27, wherein thechromium salt is chromium (III) chloride or chromium(III)acetylacetonate.

Statement 31. The catalyst system of any one of statements 1 to 4 or 28to 30, or the process of any one of statements 5 to 21 or 28 to 30,wherein the an N²-phosphinyl bicyclic amidine has Structure NPBA 1, NPBA2, NPBA 3, NPBA 4, or NPBA 5

and the N²-phosphinyl bicyclic amidine chromium salt complex hasStructure NPBACr 1, NPBACr 2, NPBACr 3, NPBACr 4, or NPBACr 5

All publications and patents mentioned herein are hereby incorporated intheir entirety by reference into the present disclosure. Thepublications and patents mentioned herein can be utilized for thepurpose of describing and disclosing, for example, the constructs andmethodologies that are described in the publications, which might beused in connection with the presently described subject matter. Thepublications discussed throughout the text are provided solely for theirdisclosure prior to the filing date of the present application. Nothingherein is to be construed as an admission that the inventors are notentitled to antedate such disclosure by virtue of the results of priorinvestigations, including but not limited to experimental results.

Therefore, the present disclosure is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Thisconcludes the detailed description. The particular embodiments disclosedabove are illustrative only, as the subject matter of the presentdisclosure can be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above can be altered or modified and all suchvariations are considered within the scope and spirit of the subjectmatter of the present disclosure. Accordingly, the protection soughtherein is as set forth in the claims herein.

What is claimed is:
 1. A catalyst system comprising: i) (a) anN²-phosphinyl bicyclic amidine chromium salt complex having StructureNPBACr I or Structure NPBACr II

or (b) a chromium salt and an N²-phosphinyl bicyclic amidine havingStructure NPBA I or Structure NPBA II

wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently are ahydrogen or a C₁ to C₃₀ organyl group, L¹ and L² independently are a C₁to C₃₀ a hydrocarbylene group, R⁴ and R⁵ independently are a C₁ to C₃₀organyl group and R⁴ and R⁵ optionally are combined to form L⁴⁵ forminga ring or ring system including the phosphorus atom where L⁴⁵ is a C₁ toC₃₀ organylene group, CrX_(p) is a chromium salt wherein X is amonoanion, and wherein p is an integer from 2 to 6; and ii) anorganoaluminum compound.
 2. The catalyst system of claim 1, wherein thechromium salt is a chromium(III) carboxylate, a chromium(III)β-diketonate, or a chromium(III) halide.
 3. The catalyst system of claim1, wherein the chromium salt is chromium(III) chloride or chromium(III)acetylacetonate.
 4. The catalyst system of claim 1, wherein theorganoaluminum compound comprises an aluminoxane.
 5. The catalyst systemof claim 4, wherein the aluminoxane comprises methylaluminoxane (MAO), amodified methylaluminoxane, ethylaluminoxane, n-propylaluminoxane,isopropylaluminoxane, n-butylaluminoxane, sec-butylaluminoxane,iso-butylaluminoxane, t-butyl aluminoxane, 1-pentyl-aluminoxane,2-pentylaluminoxane, 3-pentylaluminoxane, isopentylaluminoxane,neopentylaluminoxane, or mixtures thereof.
 6. The catalyst system ofclaim 1, wherein the catalyst system has an aluminum of theorganoaluminum compound to chromium of the chromium salt or chromium ofthe N²-phosphinyl bicyclic amidine chromium salt complex molar ratio inthe range of 10:1 to 5,000:1.
 7. The catalyst system of claim 1, whereinL¹ and L² independently are a C₁ to C₃₀ a methylene group, aneth-1,2-ylene group, or a prop-1,3-ylene group.
 8. The catalyst systemof claim 1, wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸independently are a hydrogen or a C₁ to C₁₀ hydrocarbyl group.
 9. Thecatalyst system of claim 8, wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷,and R¹⁸ independently are a hydrogen or a C₁ to C₁₀ hydrocarbyl group,L¹ and L² independently are a C₁ to C₃₀ a methylene group, aneth-1,2-ylene group, or a prop-1,3-ylene group, R⁴ and R⁵ independentlyare a C₁ to C₁₀ hydrocarbyl group and R⁴ and R⁵ optionally are combinedto form L⁴⁵ forming a ring or ring system including the phosphorus atomwhere L⁴⁵ is a C₁ to C₁₀ hydrocarbyl group, X is a monoanion, andwherein p is
 3. 10. The catalyst system of claim 1, wherein theN²-phosphinyl bicyclic amidine has Structure NPBA 1, NPBA 2, or NPBA 3

and the N²-phosphinyl bicyclic amidine chromium salt complex hasStructure NPBACr 1, NPBACr 2, or NPBACr 3;


11. A process comprising: a) contacting i) ethylene, ii) a catalystsystem comprising (a) (i) an N²-phosphinyl bicyclic amidine chromiumsalt complex having Structure NPBACr I or Structure NPBACr II

or (ii) a chromium salt and an N²-phosphinyl bicyclic amidine havingStructure NPBA I or Structure NPBA II

wherein R¹¹, R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently are ahydrogen or a C₁ to C₃₀ organyl group, L¹ and L² independently are a C₁to C₃₀ a hydrocarbylene group, R⁴ and R⁵ independently are a C₁ to C₃₀organyl group and R⁴ and R⁵ optionally are combined to form L⁴⁵ forminga ring or ring system including the phosphorus atom where L⁴⁵ is a C₁ toC₃₀ organylene group, CrX_(p) is a chromium salt wherein X is amonoanion, and wherein p is an integer from 2 to 6, (b) anorganoaluminum compound, and iii) optionally an organic reaction medium;and b) forming an oligomer product in a reaction zone.
 12. The processof claim 11, wherein the chromium salt is a chromium(III) carboxylate, achromium(III) β-diketonate, or a chromium(III) halide.
 13. The processof claim 11, wherein the chromium salt is chromium(III) chloride orchromium(III) acetylacetonate.
 14. The process of claim 11, wherein theorganoaluminum compound comprises an aluminoxane comprisingmethylaluminoxane (MAO), a modified methylaluminoxane, ethylaluminoxane,n-propylaluminoxane, isopropylaluminoxane, n-butylaluminoxane,sec-butylaluminoxane, iso-butylaluminoxane, t-butyl aluminoxane,1-pentylaluminoxane, 2-pentylaluminoxane, 3-pentyl-aluminoxane,isopentylaluminoxane, neopentylaluminoxane, or mixtures thereof.
 15. Theprocess of claim 11, wherein the reaction zone has an aluminum of theorganoaluminum compound to chromium of the chromium salt or chromium ofthe N²-phosphinyl bicyclic amidine chromium salt complex molar ratio inthe range of 10:1 to 5,000:1.
 16. The process of claim 11, wherein R¹¹,R¹², R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, and R¹⁸ independently are a hydrogen or aC₁ to C₁₀ hydrocarbyl group, L¹ and L² independently are a C₁ to C₃₀ amethylene group, an eth-1,2-ylene group, or a prop-1,3-ylene group, R⁴and R⁵ independently are a C₁ to C₁₀ hydrocarbyl group and R⁴ and R⁵optionally are combined to form L⁴⁵ forming a ring or ring systemincluding the phosphorus atom where L⁴⁵ is a C₁ to C₁₀ hydrocarbylgroup, X is a monoanion, and wherein p is
 3. 17. The process of claim11, wherein the N²-phosphinyl bicyclic amidine has Structure NPBA 1,NPBA 2, or NPBA 3

and the N²-phosphinyl bicyclic amidine chromium salt complex hasStructure NPBACr 1, NPBACr 2, or NPBACr 3


18. The process of claim 11, wherein an ethylene trimer has a 1-hexenecontent of at least 95 wt. % and/or an ethylene tetramer has a 1-octenecontent of at least 95 wt. %.
 19. The process of claim 11, wherein theoligomer product has a C₈/C₆ ratio is at least 1.5:1.